Multi-station RF thermometer and alarm system

A multi-station RF thermometer and alarm system measures temperatures and/or percent relative humidity at remote locations by RF weather stations, and displays received temperature and/or other weather data telemetry on a multi-station base station that provides out-of-bounds alarm signal indications whenever temperatures are outside of user-selectable minimum and maximum values. Randomized transmission times in one embodiment and two-phase unique transmission schedules in another lessen the possibility of on-going collisions between two or more transmitters contending for the base station at the same time. Redundant data transmission lessens the possibility of environmental noise interference. The redundant data, transmitted at random times in one embodiment, includes a unique channel ID code, house-keeping data, the current temperature and/or time-to-next-transmission data, and in another embodiment, transmitted at uniquely prescheduled times of two-phase transmission schedules, includes station location ID and transmission schedule phase. The weather parameter sensing transmitters operate at a low duty cycle with low peak current consumption resulting in long battery life. The multi-station base station may be AC- or battery-powered. Channel and station ID switches are provided on the remote temperature sensing transmitters and on the multi-station base station in one embodiment and a station ID number selection switch is provided in another transmitter embodiment.

FIELD OF THE INVENTION

This invention is drawn to the field of telemetry, and more particularly, to a novel multi-station RF thermometer and alarm system.

BACKGROUND OF THE INVENTION

Many of life's activities are heavily influenced by the temperature. Heretofore, hard-wired digital thermometers, such as the model IOTA1 and the model IOTA2 commercially available from TREND Industries, Inc., or the Electronic Weather Station With Alarm Clock, commercially available from CATHAY PACIFIC, measure temperature by a hard-wired probe, and display the measured temperature on an associated display. Such hard-wired digital thermometers, however, need to be placed within inches or feet of the environment to be measured. This can be inconvenient, as this type of digital thermometer is not placed where it is most accessible and likely to be needed (e.g., next to a bed, on a desk, etc.), but where it must be placed to work.

Wireless (RF) digital thermometers, such as the model “7055” Wireless Weather Station With Radio Controlled Clock, commercially available from Europe Supplies, Ltd., measure temperature by a remote wireless temperature station and display the measured temperature on a display associated with a base station. Although in principle such transmitters may be remotely located to the base, environmental noise sources have generally limited their practical range and have given rise to erroneous telemetry and lack of operator confidence. And if more than one location needs to be monitored, another such RF transmitter and base pair needs to be provided for every location to be measured. Not only has this resulted in increased overall costs, and undesirable multiplication of base stations, but the utility of such transmitter/base pairs has further been limited by contention-induced interference as transmissions from the multiple transmitters collide at each base station.

Moreover, both the hard-wired and RF temperature thermometers heretofore have had their utility limited by probe placement difficulties, whenever locations that are other than directly exposed and in the open are to be monitored, and by a general inability to provide information of comfort level or of weather situations that may endanger well-being.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to disclose a multi-station RF thermometer and alarm system suitable for home, office and light industrial use.

It is another object of the present invention to disclose a multi-station RF thermometer and alarm system that provides temperature monitoring of plural remote locations and at a local base station.

It is another object of the present invention to disclose a multi-station RF thermometer and alarm station that provides reliable temperature or other weather parameter, such as humidity, transmission and reception in the presence of interference (environmental noise interference and contention-induced interference).

It is another object of the present invention to disclose a multi-station RF thermometer and alarm system that provides user-setable alarm limits for each of multiple remote and/or local locations and that provides alarm signals whenever out-of-bounds conditions prevail at any location.

It is another object of the present invention to disclose a multi-station RF thermometer and alarm system that provides accurate temperature or other weather parameter, such as humidity, sensing and transmission over wide temperature, humidity and distance ranges in a manner that requires low power consumption suitable for long-life battery operation.

It is another object of the present invention to disclose a multi-station RF thermometer and alarm system that responds to temperature and humidity telemetry and provides heat index information not only useful as a general comfort indicator, but may also prove invaluable in times when high temperature and high humidity can lead to dangerous heat stroke levels.

In accord therewith, the disclosed multi-station RF thermometer and alarm system of the present invention includes at least one portable, battery-powered temperature station and a multi-station base station. Each of the at least one portable, battery-powered temperature stations provides, as desired, measurement of temperatures in rooms, refrigeration devices, pools, outdoor areas, etc., and the multi-station base station, which may be placed on a desk, at bedside, or otherwise as convenient, receives and displays, preferably concurrently, the measured temperature data received from the one or more portable, battery-powered temperature stations and measured at the multi-station base station.

In one preferred embodiment, each temperature station transmits remote temperature measurements over a two-hundred and fifty foot (250′) range to the multi-station base station and is operable over an active indoor/outdoor temperature range from minus forty degrees (−40)° F. to one hundred and fifty eight (158)° F. In this embodiment, the multi-station base station receives and displays temperature from up to four (4) remote transmitters.

Accordingly to one aspect of the present invention, the portable, battery-powered temperature station includes an analog temperature sensor providing a temperature signal representative of sensed temperature; an antenna; and a processor-controlled transmitter coupled to the antenna and to the temperature signal operative (1) to periodically convert the temperature signal to a digital representation of the sensed temperature, (2) to digitally encode a data frame having first information representative of the sensed temperature and second information representative of station ID, and (3) to transmit a predetermined integral number greater than one (1) of data frames each having said first and said second information at a random time. The randomized transmission times, and redundantly encoded temperature and transmitter ID data, cooperate to alleviate collision-induced contention and to provide reliable data transmission in noisy environments. In this embodiment, the temperature data is read every thirty (30) seconds and five (5) redundant data frames are randomly transmitted once every thirty (30) to sixty (60) seconds.

Accordingly to a further aspect of the present invention, the portable, battery-powered temperature station includes an analog temperature sensor providing a temperature signal representative of sensed temperature; an antenna; and a processor-controlled transmitter coupled to the antenna and to the temperature signal operative (1) to periodically convert the temperature signal to a digital representation of the sensed temperature, (2) to generate a schedule of present and future random transmission times, (3) to digitally encode a data frame having first information representative of the sensed temperature, second information representative of station ID, and third information representative of the schedule of present and future random transmission times and (4) to transmit a predetermined integral number of data frames each having said first, said second and said third information at a random time. The schedule of present and future random transmission times allows the multi-station base station to “sleep” at times when no transmissions are scheduled, or when previous transmissions indicate very little temperature change, thereby conserving power enabling long-life battery-powered base station operation.

According to another aspect of the present invention, the disclosed portable, battery-powered temperature station includes a housing; a waterproof probe electrically connected to the housing via an elongated flexible cable of predetermined length; an attachment member for stowing the probe to the housing when not in use; and means for paying out any selected length of the elongated flexible cable of predetermined length selected to accommodate the needs of each particular application. In one preferred embodiment, the housing includes a front wall and a battery receiving compartment, and the attachment member includes a well formed in the front wall of the housing dimensioned to frictionally receive the probe, and the pay-out means includes a wire-receiving chamber provided in the battery compartment of the housing. The selectably extendable probe enables to measure hard-to-reach areas, such as the water temperature of an outdoor pool or the inside temperature of a storage freezer.

According to another aspect of the present invention, the disclosed multi-station base station includes a multi-field reconfigurable display; operator input means; a receiver for providing an output signal in response to transmissions received from each at least one portable, battery-powered temperature station; and a processor coupled to the display, to the input means, and to the receiver, that is operative in a decode/display mode, an alarm set mode, and an alarm announce mode.

In the decode/display mode, the processor is operative (1) to configure the display with a field that corresponds to each of multiple temperature station zones, (2) to recover from the output signal of the receiver the first information representative of sensed temperature and the second information representative of the transmitting station ID for each data frame of the redundantly transmitted data frames, and (3) to display the recovered temperature data in a field corresponding to an identified station if the first information representative of the sensed temperature of two (2) of the redundantly transmitted data frames conform to each other for a given station.

In one preferred embodiment, the display is configured with a comparatively-large “active” location field, with five (5) temperature station fields (four (4) remote station and one (1) base station fields), and with temperature high and low fields, and the processor is operative in the decode/display mode to display the current temperature of any temperature station in the comparatively large “active” location field and the daily high and low temperatures in the corresponding high and low temperature fields in response to operator input station selection, and to concurrently display the temperature at any active locations (remote and/or base) in the corresponding ones of the five (5) temperature station fields. Other display configurations, such as concurrent and/or sequential display of less than all of the active locations, and operator input station display selection, could be employed.

In the alarm set mode, the processor is operative to configure the display with alarm min and alarm max fields and with at least one alarm set station field, and is operative in response to operator input station (base or remote) selection, in response to operator input alarm min and max values selection and in response to operator input alarm arming to set and to display min and max temperature bounds for each station selected and armed. Min/max setpoints for temperature range may be set for all locations. If the temperature in any location goes outside this set range, an alarm (visible, audible and/or remote) signal indication is provided in alarm announce mode. In the preferred embodiments, all stations that have been armed are concurrently displayed, although sequential display in response to operator input station display selection could be employed.

In alarm announce mode, the processor is operative to configure the display with an alarm announce icon field and at least one active alarm station field, and is operative (1) to display a location where an active alarm condition exists in the active alarm station field, (2) to provide an alarm signal indication, and (3) is operative in response to operator alarm dis-arm input to clear the alarm condition for each alarm location. The alarm signal may be an audible, a visible, and/or a remote alarm signal. In the preferred embodiments, all stations that have active alarm conditions are concurrently displayed, although sequential display in response to operator input station display selection could be employed.

In one embodiment, the multi-station base station is AC outlet powered, and in other embodiments, it is battery-powered.

In further disclosed embodiments, each portable, battery-powered weather station is operative to alternatively transmit percent relative humidity and temperature data redundantly in accord with a schedule of transmission times unique to each portable, battery-powered weather station. The redundant transmission of weather data helps prevent noise interference at the multi-station base station, and the unique schedules of transmission times both held prevent contention-induced interference at the multi-station base station as well as allow the multi-station base station to enter battery-power-conserving mode when no receptions are scheduled from each of the portable weather stations.

For each of the portable, battery-powered weather stations that measure and transmit temperature and percent relative humidity data, the multi-station base station selectably calculates and displays heat index information.

A method of encoding data at the portable, battery-powered weather stations to maximize transmission range and detection sensitivity at the battery-powered multi-station base station is disclosed.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Referring now toFIG. 1, generally designated at10is a functional block diagram of the multi-station RF thermometer and alarm system in accord with the present invention. The system10includes a plurality of RF thermometers or other weather stations12to be described and a multichannel base station14in spaced apart relation to the plural RF thermometers12. The system10is adapted for home, office and light industrial use. The RF thermometers12are portable, battery-powered devices that may be placed anywhere where temperatures are to be monitored. For example, one temperature transmitter12could be attached to the back of the house, another in the pool, a third in a green house, and a fourth in the garden, not shown.

The multi-channel base station14includes a receiver, not shown, to be described that receives the temperatures or other weather data transmitted by the plural RF thermometers12and displays temperature data received from the plural RF thermometers12on display16. The multichannel base station14also displays the temperature at the base station by means of the display16. In the presently preferred embodiments, the display16displays the temperature at the base station14, as well as the temperatures at each of the remote RF thermometers12, concurrently. Other temperature display methodologies, such as sequential display of the temperatures at plural remote and base station locations may be employed.

The multichannel base station14monitors the temperature data received from each of the plural remote RF thermometers12and the base station14and compares the received temperatures and the base station temperature to user-setable alarm limits to be described for each remote location and the base station. In the preferred embodiments, the alarm limits are minimum and maximum limits independently user setable for each location (base and remote). If the received temperatures and the local base station temperature are out of the bounds set by the alarm limits for any location, the multichannel base station14provides an alarm as schematically illustrated by box18. The alarm18in the preferred embodiment includes an audible and a visible alarm signal.

A remote dialer20is connected to the multichannel base station14. The remote dialer20is connected to a remote station22via the phone network24. The remote dialer20sends all temperature data to the remote display22at preset times, or when alarm conditions exist at any location.

The remote station22receives and displays all temperature or other data sent by the remote dialer22. The remote station22may dial the remote dialer20via the phone network24to request the current temperature data for any location, as well as the corresponding alarm limits.

The remote station22preferably includes a DTMF generator and a DTMF listener, not shown, that cooperate to send control information via the phone lines, and to receive data back from the multi-station base station in accord with the control information sent. The remote user into this way may, for example, request the current temperature information from all stations (remote and base) from the multi-station base station.

To manage interference (contention-based interference arising from the plural RF thermometers competing with the multichannel base station as well as noise interference arising in the intended operating environment), the multi-station RF thermometer and alarm system10of the present invention employs four (4) principal measures. First, each RF thermometer12and the multichannel base station14in one embodiment are provided with dual, user selectable channels “A” and “B” to be described. For example, interference from another multi-station RF thermometer and alarm system operating in the same locale may be eliminated by switching from one to the other of the two (2) channels. Second, each RF thermometer12in one embodiment transmits its temperature data at random times, preferably once every thirty (30) to sixty (60) seconds. The randomness of the transmissions makes it statistically unlikely that temperature data from multiple RF thermometers arrive simultaneously at the multichannel base station14. In another embodiment, each RF weather station12transmits its temperature and/or humidity data in accord with a schedule of transmission times unique to each weather station. Third, each RF thermometer12transmits redundant temperature and station ID information. In one embodiment, five (5) redundant data frames constitute the data telemetry. Should environmental noise sources corrupt part of the telemetry, the multichannel base station14would be able to recover any uncorrupted part thereof. Fourth, the multichannel base station14maintains a record of time of receipt for each RF thermometer12data transmission and updates temperature data received from the plural RF thermometers12provided the same is received within a predetermined time window. So long as the temperature data from each channel (station) is received within the predetermined time window, preferably fifteen (15) minutes in one embodiment and one (1) hour in another embodiment, from the time of last receipt, the multichannel base station updates the temperature information it maintains for each channel. Otherwise, it provides an indication of an inoperable channel. These channel recovery windows should be sufficient for most noisy environments, although a different duration window could be employed.

Referring now toFIG. 2, generally designated at40is an elevational view of the front of one embodiment of the RF thermometer of the multi-station RF thermometer and alarm system of the present invention. The RF thermometer40includes a water-resistant housing42having O-ring seals, not shown, a well generally designated44integrally formed in the housing42for receiving a temperature probe, and a waterproof temperature probe46shown received in the probe receiving well44. The waterproof probe46is connected to the housing42via an elongated flexible cable48of predetermined length, preferably ninety (90) centimeters. A display50for displaying the temperature sensed by the probe46is mounted to the housing42. The RF thermometer40is battery-powered, is operational from minus fifty (−50) to plus seventy (+70) Co, has a range of sixty (60) meters obstructed (i.e. through walls), an accuracy of +/− 0.5 Co and a minus forty (−40) to a plus forty (+40)Co range for reliable temperature measurement.

Referring now toFIG. 3, generally designated at60is a perspective view of the back of the portable, battery-powered RF transmitter of the multi-station RF thermometer and alarm system of the present invention with its battery door and wall mounting bracket removed. Chamber generally designated62defined in the battery receiving compartment provides a space in which the cable48may be looped and stored between batteries64. Any selected length of the cable48of predetermined length may be payed-out of the chamber42to allow the waterproof probe46to reach intended temperature measurement locations as determined by the needs of each particular applications environment.

As shown, channel “A” and “B” selector and station ID switches66,68are preferably mounted in the battery compartment, although any other suitable location therefor could be employed.

Referring now toFIG. 4, generally designated at70is a functional block diagram of the portable, battery-powered RF thermometer of the multi-station RF thermometer and alarm system of the present invention. Digital controller72, operatively connected to RAM memory and ROM memory, not shown, is connected to channel setting and station identifying DIP switches74, temperature sensor76, LCD display78, and a three hundred and fifteen (315) megahertz RF oscillator80. The channel set switches74preferably are two (2) DIP switches (containing four (4) SPST switches each), each for channel “A” and for channel “B”. In use, each RF thermometer is set to a different four (4) bit ID code on either channel, and the receiver is set to either bank A or bank B. This minimizes the problem of interference from a neighboring multi-station RF thermometer and alarm system, and/or from environmental sources of interference. Although channel selecting and station identifying DIP switches are presently preferred, other channel setting and/or station identifying means in the transmitter could be employed.

The controller72preferably is a OKI Semiconductor MSM64162 microcontroller (with internal RAM and ROM). The temperature sensor76preferably is a Semitec 103AT-2B thermistor. The LCD display78preferably is a custom-manufactured display.

The controller72(1) measures the resistance of the thermistor of the temperature sensor76and numerically calculates the temperature corresponding thereto, (2) encodes a data packet having redundant first data representative of the sensed temperature and redundant second data representative of the transmitter ID and (3) controls the RF oscillator80to transmit a data frame having the encoded data packets at random time. In addition, the controller72performs the functions of displaying the temperature on the liquid crystal display78and checking the battery voltage.

In one preferred embodiment, the controller72transmits eight hundred eighty five (885) millisecond data packets on a randomized schedule of approximately twice per minute, randomly selected every thirty (30) to sixty (60) seconds, with no less than thirty seconds between transmissions. The average duty cycle of any one hundred (100) millisecond portion of the transmission does not exceed fifty (50) percent, permitting a six (6) dB increase in the peak output power from the transmitter. The eight hundred and eighty five (885) millisecond transmission consists of a preamble followed by five (5) identical data frames as shown inFIG. 5. AManchester-like encoding technique is preferably used for the data frames.

A preamble signals the start of transmission and allows the data slicer time to stabilize before the data is sent. Each data frame contains a wait (low) pulse, a sync (high) pulse, a start (low) pulse, a sixteen (16) bit channel ID word, a four (4) bit setup word and a sixteen (16) bit BCD temperature word.

The preamble is a square-wave train, consisting of twenty (20) high pulses and nineteen (19) low pulses. The wait pulse is low for two (2) bit periods. The sync pulse is high for four (4) bit periods. The start pulse is low for two (2) bit periods. The data is sent as (bit) followed by (complement of bit). Thus, the sixteen (16) bit ID word is represented by thirty two (32) bits, the four (4) bit setup word is represented by eight (8) bits, and the sixteen (16) bit temperature word is represented by thirty two (32) bits. The complete transmission is four hundred and thirty nine (439) bit periods in duration.

In another preferred embodiment, where time-of-next transmission scheduling is included in the data frames as a means of conserving power in the multi-station base station, the data frames, in addition to the preamble, channel ID, and temperature words, include time-to-next transmission information. If the “time to next transmission” is represented in seconds, six (6) bits will give zero (0) to sixty-three (63) seconds of wait time. Inclusion of these bits (and the complemented bits) adds an additional twelve (12) bits to each frame and sixty (60) bits to the complete packet, giving a four hundred ninety nine (499) bit transmission. An alternative means of specifying the “time to next transmission” is to send the number of seconds deviation from the average transmission interval. For instance, if the transmission randomly deviates by plus/minus ten (10) seconds from a nominal value of forty (40) seconds, a five (5) bit time code could be used (range 00-31 seconds or plus/minus 16 seconds). If it is desired to have a much longer interval between transmissions, the actual time and date of the next transmission(s) could be set. This could be represented in BCD digits in seconds/hr/days/month format, or by a count-down time expressed in seconds (or tens of seconds, or hundreds of seconds, and so on.) Other schemes may be employed as well without departing from the inventive concepts.

Referring now toFIG. 6, generally designated at100is a schematic circuit diagram of the RF oscillator of the portable, battery-powered RF transmitter of FIG.4. The RF oscillator includes transistor Q1in a saturated Pierce-like oscillator configuration, preferably resonant at three hundred and fifteen (315) megahertz, with frequency stabilized by SAW resonator marked “SAW1” connected to the base of transistor Q1. A loop antenna marked “LOOP ANT” is preferably etched with the oscillator on a printed circuit board, not shown. ON/OFF keying (“OOK”) modulation of the three hundred and fifteen (315) megahertz carrier is provided for by applying zero (0) and positive three (+3) volt logic levels to the data input (resistor R3) from the controller72(FIG.4). Elements R1, R2, R3, R4and R5set the operating point of transistor Q1; (R3also serves as an input port for modulating the transmitter), elements C4, C5and C6in conjunction with the loop antenna provide a tuned output network that attenuates harmonics. C3is a bypass capacitor to prevent RF energy being fed back to the controller through the data input . Element C1is a bypass capacitor to provide a low impedance path for the circulation of RF current. C2couples the output network to the collector of Q1. L1is the collector inductor.

Referring now toFIG. 7, generally designated at110is a flow chart illustrating the operation of the controller of the portable, battery-powered RF thermometer of the multi-station RF thermometer and alarm system of the present invention.

As shown by a block112, the processor is operative to initialize, and as shown by a block114, is operative to determine whether five (5) seconds have elapsed.

If five (5) seconds have elapsed, the processor is operative to check channel identification and battery status as shown by a block116. Although the processor preferably checks channel ID and battery status every five (5) seconds, other intervals could be employed.

As shown by a block118, the processor is then operative to determine whether it is time to randomly transmit its data packet of redundant data frames. Any suitable technique, such as a random number generating algorithm, may be employed.

If it is, and time-of-next transmission scheduling is employed, the processor is operative to generate a schedule of random transmission times as shown by a block120, and then is operative to transmit its data packets as shown by a block122.

As shown by a block124, the processor is then operative to determine if thirty (30) seconds have elapsed since the last temperature measurement. If thirty (30) seconds have not elapsed, processing returns to the block114. Although thirty (30) second temperature measurement intervals are presently preferred, other temperature measurement intervals could be employed.

As shown by a block126, if thirty (30) seconds have elapsed, the processor is operative to measure the temperature, and processing returns to the block114.

Referring now toFIG. 8, generally designated at130is a front elevational view of one embodiment of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention. The multichannel base station130includes a housing132, an easy-to-read multi-field reconfigurable display134mounted to the housing132, a scroll key136, a control panel schematically illustrated by bracket designated138and a control panel door140that protects the control panel138when it is not being used. The base station130includes one (1), two (2) position channel switch, a piezo audible alerter and an audible alerter disable switch, not shown. Although a channel setting DIP switch is presently preferred, other channel setting means in the receiver could be employed.

The multichannel base station130is operable in three (3) basic modes. In a decode/display mode described more fully hereinbelow, the multichannel base station130concurrently displays temperature information for each active location (remote and base), as well as displays temperature high and low information for any location selected by depressing the scroll key136.

In alarm set mode described more fully hereinbelow, the multichannel base station130allows the user to independently set alarm minimum and maximum temperature limits for each temperature location by use of the scroll key136and the set min, set max, and on/off keys142,144,146.

In alarm announce mode described more fully hereinbelow, the multichannel base station130provides audible, visible and/or remote signal indications whenever one or more monitored locations have temperature values that are out-of-bounds.

The C/F key150changes the display from centigrade to Fahrenheit in any mode.

The low/high when? key148, when depressed, displays the high and low temperatures for locations selected by the scroll key136, as well as the time when those highs and lows were registered.

The hour, minute and 12/24 keys152,154, and156set the time; and the month, day, and year keys158,160, and162set the date.

Description labels, not shown, may be provided on the inside of the door140to identify the locations of each of the one or more remote RF thermometers.

Referring now toFIG. 9, generally designated at190is a functional block diagram of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention.

A digital controller192, preferably a Samsung KS57C2616 microcontroller with internal ROM and RAM, is connected to a local temperature sensor194(preferably consisting of a OKI Semiconductor MSM64162 microcontroller and Semitec 103AT-2B thermistor), a receiver196, a multi-field re-configurable display198, control panel200, channel set switches202and to visible and audible alarms respectively designated204,206.

The local temperature sensor194preferably includes a thermistor located in the base station operative to sense the temperature in the environ thereof. Preferably, the local temperature sensor194includes a microcontroller, not shown, which measures the local temperature and sends this to the digital controller192which processes and displays the data on the display198in a manner to be described.

In one preferred embodiment, the digital controller192processes data received by the receiver196and displays data on the display198from up to four (4) remote temperature sensors, although a different number of remote temperature sensors could be employed. The controller192also monitors the keypad200, keeps track of the time and date, and checks for alarm conditions (temperature exceeding user-specified limits at any location). In one embodiment, power is supplied by an external voltage adapter, and the multi-station base station is always “on.” In another embodiment, where time-to-next-transmission data is provided, the multi-station base station is battery powered, waking-up to receive transmissions at scheduled times out of “sleep” mode. A battery backup circuit maintains the clock and user settings in event of power failure or power down. The visible alarm204, preferably an LED, and the audible alarm206, preferably a piezoelectric beeper, indicate the presence of an alarm condition.

Referring now toFIG. 10, generally designated at220is a schematic circuit diagram of the receiver196(FIG. 9) of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention. The receiver220includes a tuned circuit illustrated by dashed box222that improves selectivity. Capacitors C11, C13, C15and inductors L2, L3preferably are tuned to three hundred and fifteen (315) megahertz.

An input buffer schematically illustrated by dashed box224that minimizes radiation from the antenna is connected to tuned circuit222. Buffer224includes transistor amplifier Q3. Capacitors C12, C14couple the input signal to the base of transistor Q3, while resistors R6, R10and R14bias transistor Q3to operate in a linear manner. R6also serves as a collector load resistance. Capacitor C4is a power supply decoupling capacitor.

A demodulator schematically illustrated by dashed box226for detecting the received signal is connected to transistor Q3of the input buffer222via coupling capacitor C8. The demodulator includes transistor Q2operated as a super-regenerative detector. Resistors R3, R4, R13and R18define the operating point of transistor Q2. Capacitors C7, C15and resistors R4, R18form the quench network for the super-regenerative detector. Inductor L4serves to isolate the signal voltage from the biasing network. Resistor R15and capacitor C19provide a low-pass filter to remove quench-frequency components from the detector output, while the filtered output is coupled to the data slicer input via capacitor C17. Capacitor C1provides power supply decoupling. Inductor L1in conjunction with capacitors C5and C10form a tank circuit tuned to resonate at three hundred and fifteen (315) megahertz.

Data slicer schematically illustrated by dashed box228for extracting digital data from the detected signal is connected to the detector226. The data slicer looks at the detector output, and responds to variations about the average signal level, corresponding to the digital data stream. Operational amplifier marked “U2A” is configured as a non-inverting amplifier to boost the detected signal. Operational amplifier marked “U2B” is configured as a comparator with hysteresis (Schmitt trigger circuit). Resistors R1and R8and capacitor C17couple the demodulated signal to U2A while providing a high-pass filter to remove DC and slowly varying AC components. Resistors R5and R9set the gain of U2A. Resistors R1and R2provide a reference voltage to the non-inverting input of U2A. Capacitor C18provides power supply decoupling. Capacitor C9and resistor R11low-pass filter the signal going to the inverting input of U2B. Resistors R16and R17set the amount of hysteresis. Resistor R16also couples the U2A output to the U2B non-inverting input.

A level translator schematically illustrated by dashed box230is connected to the data slicer228. With the RF carrier ON, the data output is approximately 0.2 volts; with the RF carrier OFF, the data output is positive five (+5) volts. Transistor Q1is a clipping amplifier. Resistor R12couples the data slicer output to the base of Q1. Resistor R7is the collector resistor. Capacitor C20prevents RF energy from the digital board from being fed back to the receiver through the data output. Capacitor C6is a power supply bypass capacitor.

Referring now toFIG. 11, generally designated at240is a state diagram of the controller192(FIG. 9) of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention. As shown by a block242, the processor is operative in a decode/temperature display mode; as shown by a block244, is operative in an alarm set mode; and as shown by a block246is operative in an alarm announce mode. As shown by an arrow marked “min, max, done” extending between the decode/temperature display mode242and the alarm set mode244, the processor transitions from mode242to mode244whenever the user presses the min, the max, or the done key142,144, or146(FIG.8).

As shown by an arrow marked “on/off, 20 sec's” extending between alarm set mode244and decode/temperature display mode242, the processor is operative to transition from the alarm set mode back to the decode/temperature display mode whenever the operator depresses the done on/off key146(FIG.8), or when twenty (20) seconds of inactivity have elapsed.

Whenever an out-of-bounds alarm condition exists at any of the remote and/or base locations, the processor is operative to transition from the temperature display mode242to the alarm announce mode246as illustrated by an arrow252marked “alarm condition.”

As illustrated by an arrow marked “on/off” extending from the alarm announce mode246the decode/temperature display mode242, the processor is operative to transition from the alarm display mode to the decode/temperature display mode whenever the operator pushes the done, on/off key146(FIG.8).

As illustrated by an arrow marked “min, max” extending between the alarm announce mode246and the alarm set mode244, the processor is operative to transition from the alarm announce mode to the alarm set mode whenever the operator depresses the min key142, or the max key144(FIG.8).

With reference now toFIG. 12, which shows a pictorial diagram generally designated270that illustrates the display of the multi-field re-configurable display configured in decode/display mode, the operation of the multi-channel base station in decode/display mode will now be described. In decode/display mode, the display includes a comparatively-large active location field270and five (5) comparatively-smaller temperature station (remote and base) fields generally designated272. Each of the five (5) temperature station fields272includes a temperature field274, an alarm set field276, and a station ID field278.

A daily low icon field280, a daily low temperature field282, a daily high icon field284, and a daily high temperature field286are provided below the active location field270. Degree centigrade and degree Fahrenheit fields288,290are provided immediately to the right of the active location field270.

Time field292, and a date field294, are provided adjacent the bottom of the display.

Upon startup, the initial display is called the “idle” display which shows all temperatures for all active locations (base and remote) in the five (5) temperature station fields272, and displays the base station temperature in the active location field270. Each location is numbered “1”, “2”, “3”, “4”, and “base” in the station identification fields278. Only locations that have active data are displayed. All other locations remain blank, including their location number. All alarms are initially off. Default is degrees Fahrenheit.

A circle, not shown, around the location number is displayed in the station identification field276to indicate the active location.

The lowest and highest registered temperature in the past twenty four (24) hours (preferably reset at midnight each day) is displayed in the low and high temperature fields282,286below the active large readout temperature field270, and high and low icons are displayed in the low and high icon fields280,284. The temperature display for all locations is ° F./° C. switchable by depressing the ° C./F. key150(FIG.8), and the corresponding icon is displayed in the centigrade and Fahrenheit icon fields288,290.

If a good signal has not been received from a remote transmitter in a fifteen (15) minute period, a bad signal screen indicator (preferably, “Blank”) is displayed in that temperature location field274. If the faulty location is the active location, then both the large display readout270and the smaller temperature display272are blanked.

For the eleven (11) keys of the control panel138(FIG. 8) accessed by opening the door140(FIG. 8) on the front of the unit, pressing a key once gets you into its function and pressing it again takes you back out of the function to idle screen. The exception is for “set min” and “set max” keys142,144(FIG.8); the “alarm on/off/done” key146(FIG. 8) needs pressed to exit.

When in a set up mode (time, date, alarm), if no keys are pressed for twenty (20) seconds, then the display returns to the idle display and any changes made by the operator inside any function are saved. The exception is exiting in “alarm announce” mode, either by pressing the done/on/off key146(FIG. 8) or by pressing the min or max keys142,144(FIG.8).

The “C/F” key150and the “12/24” key156(FIG. 8) alternate between their two modes each time the key is pressed.

From idle display, the “low/high/when?” button148(FIG. 8) when pressed flashes the daily low icon in the daily low icon field280while it shows the active location temperature and the hours/minutes when this daily low temperature was recorded. After five (5) seconds, the display flashes “daily high” for five (5) seconds in the daily high icon field284and shows temperature and time of day when the daily high was reached, then returns to idle display.

The sound on/off slide switch, on the side of the unit, not shown, controls the piezoalerter206(FIG.9). In the “off” state all sounds including the key click sound is turned off.

Whenever a user presses an incorrect key a negative (5) quick beeps sound is heard and no changes are made.

When in time change mode, if the “12/24” key156(FIG. 8) is pressed, then it toggles and leaves time change mode, saves any changes made, and returns to the idle screen.

When in any set mode, if the receiver receives data from a transmitter it saves it and updates the display only after the operator exits from the set mode.

With reference now toFIG. 13, which shows a pictorial diagram generally designated300of the multi-field re-configurable display configured in “alarm set” mode, the operation of the processor in alarm set mode will now be described. The set alarms display300is generally the same as the idle display ofFIG. 12, except that the daily high and low icon and temperature fields are reconfigured to display minimum and maximum icons302,304and minimum and maximum value fields306,308; and except that a “set temperature” icon field310is provided.

When a user presses the “set min” or “set max” buttons142,144(FIG.8), the display changes from the idle display to the “set alarms” display. In the set alarms display, the active location is the only temperature shown (in the lower temperature area272and in the larger upper display area270). The daily high/low values disappear, and are replaced by the min and max alarm range temperature values in the min and max value fields306,308. When the current temperature location goes outside these values, then the alarm mode to be described for this location becomes active.

Alarm min/max values are set one location at a time. The first time the “set min” or “set max” buttons142,144(FIG. 8) are pressed, the “min” number shows five (5) degrees below the current temperature of that location and the “max” value starts at five (5) degrees above the current temperature in the min and max value fields306,308. After this, when entering new set min and set max values, the values will be the previously set values.

To set the minimum and maximum temperature targets for a location, the scroll bar136(FIG. 8) is depressed to select the location to set. In the set alarms display mode, the active location is the only temperature shown in the temperature station fields272and in the active location field270.

The set min key142(FIG. 8) is depressed once. The words “set min” start flashing in the minimum field302and “set temperature alarm” is displayed in the set temperature icon field310.

The scroll bar136(FIG. 8) is then depressed to adjust the temperature limit up or down until the desired number is reached. Adjustment occurs one-tenth (0.1) degrees at a time at a rate of two (2.0) degrees per second. When in alarm min/max set mode, the scroll rate goes to five (5) degrees/second if the scroll key136(FIG. 8) is held for more than three (3) seconds.

In a similar manner, the set max key144is depressed and the scroll bar136(FIG. 8) is then depressed to adjust the maximum temperature as well, whereupon the set max words start flashing in the max icon field304.

To exit alarm set mode, the done key146(FIG. 8) is depressed. The alarm mode is automatically switched to “on” upon exit. An icon appears in the alarm set field276beside the location number in the station identification field278to indicate that this location is now in the “on” state. At the top the display, the daily low and high temperatures being displayed for that location are replaced with the min and max set temperatures for that location while the alarm is in the “on” condition.

When in the alarm set mode the minimum temperature cannot go above the maximum temperature and the maximum temperature cannot go below the minimum. A beep is heard if min and max become equal.

With reference now toFIG. 14, which shows a pictorial diagram generally designated330of the multi-field re-configurable display configured in alarm announce mode, the operation of the processor in alarm announce mode will now be described. The alarm announce mode display330is generally the same as the alarm set display300(FIG.13), except that the set temperature icon field is reconfigured as a temperature alarm icon field332, and an LED alarm334and an audible alarm, not shown, are enabled.

If the temperature of any location goes outside the min-max alarm range and the alarm for that location has been turned on (icon displayed in the alarm set field276beside the location identifier in the station identification field278), then an alarm announce state exists and the display goes into the “alarm announce” display mode. The location with the alarm becomes the active location and is the only location that shows on the display (in the lower272and upper270display areas). The “temperature alarm” icon is displayed in the temperature alarm icon field332, and it flashes. The LED334flashes, the “alarm on” icon in the temperature alarm icon field332flashes, and if sound is “on”, the sound beeps.

To exit the alarm announce state, the operator can do several things. (All keys except min, max, and done are locked out and cannot be used). The operator can press the alarm on/off button146(FIG. 8) which turns the alarm on/off icon off and, after one (1) seconds, the display returns to idle mode display. The operator could also press either the “set min” or “set max” buttons142,144(FIG. 8) and the display immediately goes to the “set alarms” display mode and the operator may adjust the min-max range to turn off the alarm in the manner described above. If the operator leaves the “set alarm” mode and an alarm condition still exists, then the display returns to the idle display for one (1) second, then returns to the “alarm announce” display.

When a multiple alarm condition exists, then the “alarm announce” display shows all locations in the temperature station fields272that have an alarm condition. The “active” location is the location with the lowest number (e.g., “1” instead of “3”, or “2” instead of “3”, etc.; “base” location is location “0”). The operator depresses the scroll key136(FIG. 8) to handle each alarm state, one location at a time, in the manner described above. When an alarm is cleared, then after one (1) second, that location disappears from the display and the next lowest number location become the “active” location. When the last location is cleared, then the display waits two (2) seconds and returns to idle display.

If a good signal has not been received from a remote transmitter in a fifteen (15) minute period, that temperature location goes blank, indicating a bad transmission. If the faulty location is the active location, then both the large display read out and the smaller temperature display with the location number defaults to the base as the active location.

Referring now toFIG. 15, generally designated at350is a flow chart of the processor of the multi-channel base station of the multi-station RF thermometer and alarm system of the present invention. As shown by a block352, the processor is operative to determine if any temperature data is available. In one embodiment, the processor is always on, monitoring for temperature data. In another, it is “asleep,” waking up at scheduled times to monitor for temperature data. Any suitable data monitoring technique, such as an interrupt, may be employed.

If data is available, the processor is operative to determine whether two (2) frames of the redundantly transmitted data match as shown by a block354.

As shown by a block356, if two (2) frames match, the processor is operative to update the system data. System data includes the time of last receipt and the minimum and maximum received temperature values received in a twenty four hour period.

As shown by a block358, the processor is then operative to determine whether the received temperature data is out of bounds.

If it is, as shown by a block360, the processor is operative to update the display, and to transition to alarm mode as shown by a block362.

If no temperature data is available, or if two (2) frames of the redundantly transmitted data do not match for a given channel, or if there is no out of bounds conditions, the processor is operative to determine whether there has been a key press as shown by a block364.

If there was a key press on the control panel, the processor is operative to handle the key press as shown by a block366and to update system data as appropriate.

As shown by a block368, if the keypress input changed operating mode, the processor is operative to transition to alarm set mode as shown by a block368.

As shown by a block370, the processor is then operative to determine whether any data is older than fifteen (15) minutes since the last temperature data was received.

If it is, the processor is operative to blank the record as shown by a block372.

As shown by a block374, the processor is then operative to update the display, and processing returns to the block352.

Referring now toFIG. 16, generally designated at400is an elevational view of the front of another embodiment of the RF weather station of the multi-station RF thermometer and alarm system of the present invention. The RF weather station400includes a water-resistant housing402, a first weather parameter sensing probe connected to the housing402via an elongated flexible waterproof cable that senses temperature, not shown, a second weather parameter sensing probe within housing402that senses percent relative humidity, not shown, and a display404. Like the embodiment described above in connection with the description ofFIGS. 2 and 3, a chamber, not shown, is provided in the housing402in which the cable of the temperature probe may be stowed and payed-out to allow the probe to reach intended temperature measurement locations as determined by the needs of each particular applications environment. A weather station location identification switch, preferably a sequential select switch, not shown, is mounted to the housing402to allow user selection of weather station location number, and a Centigrade/Fahrenheit switch, not shown, is mounted to the housing402to allow user selection of temperature scales. The display404displays the temperature sensed by the selectably extendable first probe mounted to the housing, and displays indicia representative of the selected weather station location number, and of the temperature scale selected. The display404also displays indicia representative that a data packet to be described is being telemetered. The RF weather station400is battery-powered, is operational from minus forty (40) degrees Fahrenheit to one hundred twenty-two (122) degrees Fahrenheit, and has a range of up to about two hundred fifty (250) feet.

Referring now toFIG. 17, generally designated at420is a functional block diagram of the portable, battery-powered RF weather station of the multi-station RF thermometer and alarm system of the present invention. Digital controller422, operatively connected to RAM memory424and ROM memory426, is connected to sequential-select station identifying switch428(and Centigrade/Fahrenheit scale select switch), temperature sensor430, humidity sensor432, LCD display434, and to the three hundred fifteen (315) MHZ oscillator436described above in connection with the description ofFIGS. 4 and 6, not separately described again for the sake of brevity of explication. In use, each RF weather station is set to a different station identification number by the sequential-select station identifying switch428. The ROM426includes plural unique transmission schedules to be described, another one of which is selected for each setting of the sequential-select station identification switch428. For the three (3) station identification switch settings of the preferred embodiment, another one of three (3) unique transmission schedules, preferably {60 seconds+/−1 second}, {60seconds+/−5 seconds}, and {60 seconds+/−10 seconds}, is selected. For example, location “3” will transmit repetitively alternately at fifty (50) seconds and seventy (70) seconds. Although two-phase repeat schedules are presently preferred, more than two (2) phase schedules, one-time phase offsets at the time of start-up to promote substantially contention-free reception, or other unique schedules to substantially preclude contention-induced interference at the receiver and to allow the receiver to enter low-power mode until the time of next transmission, could be employed without departing from the inventive concepts.

The controller422preferably is the OKI Semiconductor MSM64162. The temperature sensor430preferably is the Semitec 103AT-2B thermistor. The humidity sensor preferably is the Shinyei Kaisha C5-M3 humidity sensor. The LCD display434preferably is a custom-manufactured display.

The controller422(1) measures the resistance of the thermistor of the temperature sensor430and numerically calculates the temperature corresponding thereto, (2) measures the resistance of the humidity sensor432and calculates the humidity corresponding thereto, (3) encodes a data packet having first data representative of data type, weather station ID and phase of the two-phase transmission schedule, and redundant second data representative of weather parameter sensed, and (4) controls the RF oscillator436to transmit the data frame having the encoded data packets at preselected times. In the preferred embodiment, the controller422alternatively transmits temperature data and humidity data in sequential data packets, although any other method may be selected for telemetry of multiple weather parameter data. The controller422performs the functions of displaying the temperature on the liquid crystal display434and the indicia representative of station identification, active transmission, temperature scale selected, as well as checks the battery voltage.

In the preferred embodiment, the controller422transmits in accord with the particular unique transmission schedule selected approximately once per minute. The average duty cycle of any transmission does not exceed twenty-five (25) percent, permitting a twelve (12) dB increase in the peak output power from the transmitter. The transmission consists of a preamble, a sync word, and a setup word followed by two identical data frames, as shown in FIG.18.

A modified Manchester-like encoding technique that maximizes receiver sensitivity and provides higher output peak power than the embodiment ofFIGS. 2-7is preferably used for the entire transmission, where a “1” is represented by the pulse sequence “1000” and a “0” is represented by the pulse sequence “0100.” The “1” in each pulse sequence indicates the transmitter is pulsed on for four and one-half (4.5) milliseconds, while the “0” indicates that the transmitter is turned off for four and one-half (4.5) milliseconds. This coding technique in accord with the present invention provides the twenty-five (25) percent duty cycle, and its accompanying improvement in higher output peak power, and also insures that the transmitter cannot be on for more than one (1) consecutive four and one-half (4.5) millisecond interval, which helps to maximize receiver sensitivity by minimizing “ripple” in the data slicer circuit.

For example, if a digital “7” is to be sent, which is “0111” in standard BCD representation, it first is transformed in accord with the modified Manchester encoding technique of the present invention, and transmitted as “0100 1000 1000 1000.” It takes sixteen (16) pulses instead of four (4) bits as a bit is represented by four (4) pulses. Since there are only four (4) high pulses (1's) and twelve (12) low pulses (0's), the average energy output is twenty-five (25) percent “on” and seventy-five (75) percent “off.” When data is joined, two “1's” are never present side-by-side as a zero (0) is always at least at one end. This maximizes receiver sensitivity. High pulses butted together become a single double-duration pulse, which has the undesirable effect of increasing voltage ripple in the data slicer, thus degrading its sensitivity. This undesirable effect is overcome by the encoding technique of the present invention, which makes the data look as much as possible like a continuous stream of “1000 1000 1000 1000 1000 . . . . ”

The preamble is a string of “1000 1000 1000 . . . ” followed by the sync pulse which is two (2) high periods in length. The redundantly encoded weather data immediately follows.

Example of Complete Transmission:

Referring now toFIG. 19, generally designated at440is a flow chart illustrating the operation of the controller of the portable, battery-powered RF weather station of the multi-station RF thermometer and alarm system of the present invention.

A shown by block442, the processor is operative to initialize and to determine the number and kind of weather parameter sensors and the station identification number.

A shown by block444, the processor is operative to measure the value of the active sensors. In the preferred embodiment, where temperature and humidity sensors are present, the processor is alternatively operative to measure temperature and humidity preferably every five (5) seconds.

As shown by block446, the processor is operative to convert measured sensor data to a corresponding temperature and/or humidity weather parameter. Preferably, the processor of the transmitter of each battery-powered weather station computes the relevant weather parameter, thereby off-loading that task away from the processor of the receiver, although unconverted sensor data could be transmitted.

As shown by block448, the processor is operative to display the current temperature data and the location identification number.

As shown by block450, the processor is then operative to determine the time-to-next transmission and waits until that time as shown by block452.

As shown by block454, the processor then transmits the encoded data packet at the prescheduled time, and processing returns to block444.

Referring now toFIG. 20A, generally designated at460is a front elevational view of another embodiment of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention. The multichannel base station460includes a housing462, an easy-to-read multi-field re-configurable display464mounted to housing462, a scroll-up and scroll-down key466, a daily high/low and temperature alarm setting key468, and a reset/heat index key470. The display464includes a comparatively-large, upper portion and a comparatively-smaller, lower portion. The enlarged display portion shows the temperature of a selected active location, (or selectably its heat index if that location monitors both temperature and humidity), and the smaller display portion simultaneously shows for each of the remote weather stations and the base station as identified by the illustrated “1,” “2,” “3,” and “base” indicia the current temperatures (or percent relative humidity, for location(s) that monitor both temperature and humidity, as indicated by the icon “%” for location “2” inFIGS. 20A, B). An indication as shown by the “triangle” icon above location “2” is provided as to which location is currently selected for display in the upper portion. Depression of the scroll key466selects an active location for display in the upper portion of the display464, as shown inFIG. 20B, and depression of the daily high/low and alarm setting key468displays daily low, daily high, alarm min, and alarm max for any selected active location in the lower portion of the display464, as shown in FIG.20C. Depression of the reset/heat index key470displays the numeric value of the heat index in the upper portion of the display464for a selected active location and the indicia “heat index,” not shown, and depression of the reset/heat index key470following depression of the daily high/low and alarm setting key468resets the period during which the daily high and daily low values are recorded. A temperature alarm “on” indicator illustrated by a “bell” icon in the upper left corner of the display464indicates temperature alarm “armed” status. Below that, a radio transmission indicator illustrated by icon “(.)” and a temperature trend indicator illustrated by the upwardly directed “arrow” in the upper portion of the display464respectively indicate when telemetry is being received and the direction and speed of temperature change of any active location selected. A flashing “bell” icon is shown in the lower portion of the display464for any active location that has an out-of-bounds alarm condition. A low battery indicator and a temperature alarm LED, both not shown, respectively provide an indication of low battery power and a visible indication of an out-of-bounds alarm condition. A piezoalerter, not shown, provides an audible indication of an out-of-bounds alarm condition. A temperature scale selector switch, an alarm on/off key, and a sync key, all not shown, are respectively provided to select temperature scale, turn alarm mode on/off, and initiate sync mode whenever, for example, new remote weather stations are added or it is otherwise desirable to(re)acquire remote weather station's telemetry. Opposite the “bell” icon, indicia, such as the illustrated “F,” shows the temperature scale selected.

Referring now toFIG. 21, generally designated at480is a functional block diagram of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention.

A digital controller482, preferably a Samsung KS57C2308/16 microcontroller with internal ROM and RAM, is connected to a local temperature sensor484(preferably consisting of the OKI Semiconductor MSM64162 microcontroller and the Semitec 103 AT-2B thermistor), the receiver486(described above in connection with the description ofFIG. 10, not separately described again for the sake of brevity of explication), multi-field re-configurable display488, keypad490, and to visible and audible alarms respectively designated492,494. The controller482is battery-powered, and turns the receiver486“on” and “off” at times scheduled to receive transmissions from active locations as determined by reception clocks496. For the presently preferred embodiment that monitors telemetry from three (3) remote weather stations of the type described above in connection with the description ofFIGS. 16-19, three (3) reception clocks are maintained, but a different number could be employed in accord with the present invention.

Referring now toFIG. 22, generally designated at500is a state diagram of the controller482(FIG. 21) of the multichannel base station of the multi-station RF thermometer and alarm system of the present invention. As shown by a block502, the processor is operative in a decode/display mode; and as shown by a block504, is operative in an alarm set mode.

In decode/display mode, the controller is operative to identify which remote locations are active and to set the reception clocks496(FIG. 21) for each location identified as active. Once active locations are acquired, the controller powers-down the receiver486(FIG. 21) except at times when transmissions are scheduled, which conserves battery power and provides long-life operation. When transmissions are scheduled, the controller powers-up the receiver486(FIG.21), decodes received data packets, and updates the display when received telemetry is in proper format and the redundantly transmitted data frames match. It powers-down the receiver thereafter, or if there is no data frame match, or if the data format is improper. It lowers its clock speed when it powers-down the receiver, also to conserve battery power and improve useful battery life; vice versa, it raises its clock speed when transmissions are expected. The controller in decode/display mode handles key presses; monitors and displays temperature trends; maintains a record, and selectably displays, the daily high and low values for active locations; monitors and displays out-of-bounds alarm conditions; selectably displays the heat index; as well as provides the other audible and visible indicators described above in connection with the description of FIG.20.

When a temperature alarm sounds in decode/display mode, there are two (2) ways to turn the alarm “off.” Either the alarm on/off button is depressed to turn the alarm function “off” for all active locations, or the active alarm location is selected and the daily temperature/alarm set button is depressed to reset the alarm bounds in alarm set mode to be described.

Whenever the heat index key is depressed in decode/display mode, the controller is operative to calculate and display heat index for the active location selected. Heat index is a more accurate measurement of comfort than temperature alone, i.e., it provides “apparent temperature,” what the temperature really feels like. It not only is a useful comfort indicator, but it may prove invaluable in times when temperature and humidity can lead to dangerous heatstroke levels. For example, with a temperature of one hundred (100) degrees Fahrenheit and a relative humidity of sixty (60) percent, the temperature will actually feel like one hundred thirty (130) degrees Fahrenheit. Preferably, the following algorithm is used to calculate heat index. HI=−42.379+(2.04901523*T)−(0.22475541*T*H)−(0.00683783*T*T)−(0.05481717*H*H)+(0.00122874*T*H)+(0.00085282*T*H*H)−(0.00000199*T*T*H*H), where “HI” is heat index, “T” is temperature in degrees Fahrenheit and “H” is percent relative humidity.

Although heat index could be calculated for each combination of humidity and temperature, it is preferred that a look-up data table, not shown, be employed for this purpose.

As shown by an arrow marked “alarm ‘on/off’” extending between the decode/display mode502and the alarm set mode504, the processor transitions from mode502to mode504whenever the user presses the alarm “on/off” key. To set or reset temperature alarm limits in alarm set mode upon depression of the alarm on/off button, the scroll key is depressed to select an active location for which alarm limits are to be set. The daily temperature/alarm set button is depressed to display daily high/daily low temperatures and temperature alarm lower and upper limits in the lower portion of the display464(FIG.20); the alarm min icon will flash showing it is in “set” mode. The scroll keys are depressed to adjust the lower temperature alarm limit. After that has been set, depression again of the daily temperature/alarm set button accepts the lower range limit, and the alarm max field icon will then start flashing. The scroll keys are again depressed to adjust the upper temperature limit. Depression of the daily temperature/alarm set button accepts that value, and as shown by the arrow extending from the alarm set mode504to the decode/display mode502, the controller returns to the decode/display mode502.

Referring now toFIG. 23, generally designated at510is a flowchart of the processor of the multi-channel base station of the multi-station RF thermometer and alarm system of the present invention. As shown by block512, the processor is operative to identify active locations, set the reception clocks for each active location identified, and to extract valid weather data. As shown by block514, the processor then displays the temperature and/or humidity weather data recovered for each active location on the display.

A shown by block516, the processor is next operative to determine whether a predetermined interval, preferably three (3) minutes, has elapsed. If the time interval expired is less than the predetermined interval, processing returns to block512. After the elapse of the predetermined interval (or if maximum number of locations have been found), the processor powers the receiver down as shown by block518. Although a three (3) minute sync period to acquire active locations is presently preferred, other intervals could be employed.

As shown by block520, the processor is next operative to determine if a key has been depressed. If it has, the processor is operative to handle the keypress and to update system data as appropriate, as shown by block522. If the key is the sync key, processing branches to block512, and if the key is the alarm on/off key, processing jumps to alarm set mode as shown by block524.

Otherwise, the processor as shown by block526is operative to determine if the current time is equal to any one (1) of the reception clocks time's. If it is, the processor is operative to power the receiver up (and to raise its clock rate) as shown by block528and to determine if data is available as shown by block530. If it is, the processor is operative to determine whether the redundantly transmitted frames match as shown by block534, and updates system data and compensates the reception clocks for drift as shown by block536. The processor is then operative to determine whether the temperature data is out-of-bounds for any active location as shown by block538and, if it is, to update system data as shown by block540and to power the receiver down (and lower its clock rate) as shown by block532. But if no data is available, or if the redundant frames do not match, or if the temperature data is not out-of-bounds, the processor is operative to power the receiver down (and lower its clock rate) as shown by the block532.

Otherwise, the processor is operative to determine whether any records are older than one (1) hour as shown by block540. If not, the processor updates the display as shown by block544. If they are, the processor is operative to blank those records as shown by block542, and then to update the display as shown by the block544. The processor then handles other functions, not shown, such as the temperature trend function, whereafter processing returns to block520.

Many modifications of the presently disclosed invention will become apparent to those of skill in the art without departing from the inventive concepts. For example, other modulation methods such as frequency-shift keying or phase-shift keying could be employed. Different data encoding schemes, weather information other than temperature such as humidity and/or pressure and/or sun shine, and different duty cycles could also be employed.