DBK74-Channel Frequency-Input CardFeatures• Provides four frequency-measurementchannels• Programmable from 1 Hz to 950 kHz  per channel• Provides frequency resolution to0.00025 Hz• Accommodates low-level, high-level,
or digital inputs• Provides per-channel, user-configurable low-pass filters• Ideal for making RPM measurements
and monitoring flow meters
The DBK7 frequency-input card provides
IOtech’s data acquisition systems with fourchannels of frequency-measurement capability. The card measures the input signal’s
frequency and converts the frequency toa voltage, which can then be measured by
the data acquisition system. The DBK7’soutput is read by the data acquisition
system along with any other analog channels included in the analog scan group,
allowing easy correlation of readings fromthe DBK7 with other test parameters. The
DBK7 is particularly useful for making
RPM measurements in applications suchas automotive testing, or the monitoringof flow meters. As many as 64 DBK7s canbe connected to one data acquisition system for a total of up to 256 channels. The
DBK7 accepts low- and high-level ­analogsignals, as well as digital ­signals.
Analog Inputs. The DBK7 accepts ACcoupled analog inputs up to 80V p-p. Eachof its channels is equipped with a low-pass
input filter that is jumper selectable for
100 kHz, 300 Hz, or 30 Hz. The card can accommodate 1 Hz to 100 kHz ­measurementof signals from 50 mV to 80V p-p.
Digital Inputs. The DBK7’s digital inputs,
which can measure signals from 0.001 Hzto 950 kHz, feature TTL Schmitt-trigger
levels and can accept DC-coupled signals
from -15V to +15V. The DBK7’s digitalinputs are equipped with pull-up resistors
for use with relays or switches.

Measurement Computing

See DBK55 for module version of this board

The 4-channel DBK7 provides frequency-measurement capability
Frequency Range. The DBK7 provides
12-bit resolution at any frequency from
1 Hz to 950 kHz. Its software programmable
range selection feature allows you to define
minimum and maximum frequencies forconversion. This range is set on a per-­channel
basis and can extend over the full range ofthe card or be reduced to a frequency difference of 1 Hz or 1% of the maximum input
frequency, whichever is greater. For example,
you can configure one channel for 59.5 Hz
to 60.5 Hz, another for 495 kHz to 500 kHz,and yet another for 1 to 950 kHz. Whenfrequencies from 1 Hz to greater than 500
Hz are measured, a corresponding output
voltage is generated 250 to 500 times persecond; when frequencies from 1 Hz to lessthan 500 Hz are measured, they are updated
once per cycle.
Update Rates. Since the DBK7’s resolution
is 12 bits regardless of the range selected,
update times vary depending upon therange selected. For ranges from 1 Hz tothe user-defined maximum upper range
boundary, the voltage conversion updatewill occur every 2 to 4 ms or the period of
the input frequency, whichever is greater.
With a range of 0 to 10 kHz, the DBK7 willupdate every 2 to 4 ms. If the range is 0 to(508) 946-5100

160 Hz, the output will update every cycle or16.6 ms. As the conversion range becomes
more narrow — for example, from 49 to51 Hz — the time to resolve the 2 Hz
­differential to 12-bit resolution increases;in this example, the conversion time wouldbe a­ pproximately 59 ms.
Incoming Signal Noise. In addition to its
low-pass filter, the DBK7 has a predefinedhysteresis level built into each channel; thishelps eliminate false counting caused byhigh-­frequency noise. A programmable debounce is provided with times of 0.6 ms, 2.5ms, and 10 ms; this is for ­electromechanicaldevices such as switches or relays, whichbounce or chatter while switching.
Auto-Calibration. The DBK7 is automatically calibrated upon initialization to compensate for data acquisition system errors
and to ensure system accuracy.

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DBK7Specifications & Ordering Information
DBK7 Frequency-Input Card Block Diagram+527K Ohm

Digital.33 µf
AnalogOne of four channels

Selectableattenuator

P1Low-passfilter1220K Ohm
Frequency
measurement
12Ch. 012Ch. 112Ch. 212Ch. 3Specifications

Operating Temperature: -30 to +70 ˚CConnector: DB37 male, mates with P1*; BNC ­connectors
for signal inputs
Number of Channels per Card: 4Maximum Cards per System: 64
Frequency-to-Voltage Ranges: Programmable from
1 Hz to 950 kHz digital; 1 Hz to 100 kHz analog
Temperature Coefficient: 10 ppm for every degree
outside the range of 0 to 50 ˚CAccuracy: 0.1%
Low-Pass Filters: 300 Hz and 30 Hz
Debouncing: off 0.6, 2.5, and 10 ms

Input Characteristics

High-Level Analog Signals
Minimum: 1.25V guaranteed, 0.75V typ
Maximum:  80V p-p sine wave
Minimum Slew: 50V/s
Hysteresis: 250 mV
Impedance: AC-coupled (0.33 µF), in series with
20 kOhm to ground
Digital Signals
Input Voltage: -15V to +15V
Threshold Voltage (low): 0.8V typ, 0.5V minThreshold Voltage (high): 1.6V typ, 2.1V max
Hysteresis: 400 mV min
Pulse Width (high or low): 520 ns min
Input Impedance: 27 kOhm pull-up to +5V inparallel with 50 pF
Power Consumption:  420 mW

Low-Level Analog Signals
Minimum: 100 mV guaranteed (50 mV typ)
Maximum:  80V p-p sine wave
Minimum Slew: 5V/s
Hysteresis: 15 mV
Impedance: AC-coupled (0.33 µF), in series with
20 kOhm to ground; see block diagram

DAC

Mux
Channel selectOrdering Information
Description
4-channel frequency-to-voltage
input cardPart No.
DBK7Cables
For use with DBK10, use CA-37-x ribbon cable, orcontact factory of additional cabling options
For use with DBK60 or LogBook/360, no cable isrequired (except from DBK60 or LogBook/360 tothe A/D mainframe)
For use with no enclosure, use CA-37-x where x is thenumber of DBK devices attached
For use with DaqLab Series (internal slots), use
CA-255-2T with one board, or CA-37-2 for use with
two DBK cards (or contact factory for additional
cabling options)

Product Compatibility✔ LogBook✔ DaqBook✔ DaqLab✔ DaqScan✔ DaqBoard/2000 Series* Attachment to the DaqBoard/2000 Series requires a DBK200, DBK202, DBK203A, DBK209, DBK213, orDBK214

Measurement Computing(508) 946-5100

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