2/3. O 3

NBSIR 75-758

Operational Manual for Microwave

Hygrometer Model III

Daniel P. Stokesberry

Product Engineering Division

Institute for Applied Technology

National Bureau of Standards

and

Saburo Hasegawa

Heat Division

Institute for Basic Standards

National Bureau of Standards

July 1975

Final Report

Prepared for Naval Air Systems Command

Department of the Navy

Washington, D. C. 20360

NBS 75-758

OPERATIONAL MANUAL FOR MICROWAVE

HYGROMETER MODEL III

Daniel P. Stokesberry

Product Engineering Division

Institute for Applied Technology

National Bureau of Standards

and

Saburo Hasegawa

Heat Division

Institute for Basic Standards

National Bureau of Standards

July 1975

Final Report

Prepared for Naval Air Systems Command

Department of the Navy

Washington, D. C. 20360

U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

Table of Contents

Page

1. General 1

2. Cavity 3

3. Frequency Lock Circuitry 3

4. Temperature Control Circuitry ... 4

5. Operation 6 5.1 Temperature Controls . 6 5.2 Cavity Drying 6 5.3 Zero Reading 7 5.4 Sample Gas Measurements 7 5.5 Summary of Operating Procedure .... 8

6. Calibration 10

6.1 Dew Point Calibration . 10

6.2 Vapor Pressure Calibration 11

i
List of Figures

Figure 1 Flow diagram

V Figure 2 Block diagram of the measurement circuitry

Figure 3 Block diagram of the lock circuit

Figure 4 Schematic Lock Loops

Figure 5 Block diagram temperature control circuit

Figure 6 Schematic diagram temperature control circuit

Figure 7 Schematic diagram zero crossing detector

Figure 8 Front compartment

Figure 9 Exterior view

Figure 10 Interior view of the oven compartment

Figure 1

Wiring diag ram

List of Tables

Table 1 Delta R vs dew/frost point

Table 2 Delta R vs vapor pressure

Wiring List

Output Connector Pin Assignments

ii
Ab s t rac

This is an operational manual for the NBS microwave hygrometer,

Model III. It covers the design, operation and performance of

the hygrometer. It is capable of measuring water vapor equivalent

to the dew/frost point range of 40°C to -53 C.

When compared with the NBS two-pressure humidity generator over

the dew/frost point range of 40 C to -53 C, the following estimates

of the one sigma random errors were obtained:

a) 0.02°C for dew points 40°C to 20°C

b) 0.03°C " " " 20°C to 0°C

c) 0.09°C " frost points 0 C to -27°C

d) 0.60°C " " " -27°C to -53 C

iii

1 General

The hygrometer contains two microwave cavities. The

resonance frequency of each cavity is determined by its

dimensions and geometry, and environmental factors including

temperature, pressure, and the refractive index of the medium.

Sample air is drawn through the instrument in such a manner that

the air within each cavity is at the same total pressure and

temperature; however, one cavity is exposed to the moist test

air and the other is exposed to the same air sample with all the

water vapor removed. Under these conditions the resonance

frequency of the sample cavity (moist air) differs from that of

the reference cavity (dry air) by an amount proportional to the

water vapor content of the sample air.

Each cavity is maintained at the same constant temperature

to insure dimensional stability and the gas in each is also

maintained at the same constant temperature and equal pressure

through the technique illustrated in Figure 1. The sample air

heater raises the temperatur,e of the air to 59.9°C. The air

then flows through a coiled stainless steel tubing which brings

it up to the oven and cavity temperature of 60° + .03°C and

through the sample cavity. Most of the air exits the sample

cavity directly through the vacuum pump. A small part of the

air flows through a dryer and then into the reference cavity

before exiting the system through the vacuum pump.

The equation for the refractive index, n, of moist air for

a fixed temperature, Essen and Froome and Smith and Weintraub , can be expressed in the form:

(n-1) 10

6 = AP

X + BP

2 + CP

3

, where P^ = partial pressure of dry air,

P^ = partial pressure of carbon dioxide,

P^ = partial pressure of water vapor, and

A, B, and C * constants.

Essen, L. and K • D. Froome, The Refractive Indices and Dielectric

Constants of Air and its Principal Constituents at 24,000 MC/S,

Proc. Phys. Soc, B64 862 ( 1951).

Smith, E. K. Jr., and S. Weintraub, The Constants in Equation

for Atmospheric Refractive Index at Radio Frequencies, J. Res.

NBS 50, 39 (1953) RP2385.
For the case of two identical microwave cavities filled

with air at the same total pressure, temperature and partial

pressure of carbon dioxide, and using the relationship n = f /f,

the difference in frequency between the two cavities is:

Af

7-f- = kp3>

s where A f = resonance frequency of the reference cavity minus

the resonance frequency of the sample cavity,

f = resonance frequency of the cavity under vacuum,

f r = resonance frequency of the reference cavity,

f = resonance frequency of the sample cavity, and

K constant

The following approximation (good to better than 0.1%) can

be made for the range of frequency used:

f *

Af 7-f-- KP3- o r s Therefore, a shift in the resonance frequency of the sample

cavity is proportional to the water vapor content of the sample

air.

The major change in the new instrument, Model III, compared

to Model 1

1 ^ i s the modification of the basic measurement

method to eliminate components which are subject to mechanical

wear or sensitive to mechanical shock or vibration. The new

measurement method requires no moving parts and consists of

electronic circuitry which directly measures the frequency

difference between the two cavities.

A block diagram of the electronic circuit is shown in

Figure 2. Each microwave cavity is fed by a separate microwave

oscillator. The frequency of each oscillator is controlled by a lock circuit which forces the oscillator to stay at the

resonance frequency of the cavity. The outputs of the two

oscillators are fed to a microwave mixer. The frequency of the

mixer output is equal to the difference in frequency between its

two inputs. This signal is fed to a counter which displays the

frequency difference between the two cavities.

Hasegawa, S. and D. P. Stokesberry, An Automatic Digital Microwave

Hygrometer, Rev. Sci. Instrum. A_6 , 867 (July 1975 ).

2
2. Cavity

The two cylindrical cavities are milled into a single block

of invar (107.95mm x 63.50mm x 65.84mm). Each cavity is capped

by stainless steel endplates which are designed to temperature

compensate the cavity; this reduces the change in resonance

frequency due to a change in temperature. Air inlet and outlet

ports are milled into the endplates. The physical dimensions of

the cavities are chosen so that each cavity will resonate in the

TE Q,2 m °d e at 10.7 GHz with a Q of 10,000 and an insertion loss

of aDout 8 dB. The cavities are sealed, quartz windows provide

coupling into and out of the cavities. The isolators buffer the

cavities from its electrical environment. Video detector diodes

are mounted at the electrical outlet port of each cavity.

3. Frequency Lock Circuitry

A block diagram of one of the lock circuits is shown in

Figure 3. The operation of the loop can be understood by

opening the two feedback loops, i.e., by breaking both the

connection between the second dc amplifier and the power supply

and the connection between the first dc amplifier and the

summing network. The frequency of the microwave oscillator is

controlled by the voltage of the power supply and by the voltage

from the summing network into its modulation port. When the

loops are open, the oscillator is "free running"; its frequency

can be adjusted by turning a mechanical tuning screw so that it

is close to the resonance frequency of the cavity. A small ac signal from the local oscillator is fed through the summing

network to the microwave oscillator. This causes frequency

modulation of the microwave signal. The microwave cavity acts

as a discriminator; it changes the fm signal into an amplitude

modulated signal. The video detector senses the amplitude

modulation of the microwave signal. The signal at its output is

composed of a combination of a 200 kHz sinewave and the

harmonics of this frequency. This signal is amplified by a narrow-band ac amplifier which rejects the harmonics. The

amplified signal is fed into a phase sensitive detector. The

reference phase information for the phase sensitive detector is

obtained from the local oscillator. The output of the phase

sensitive detector is a dc voltage which is positive if the

frequency of the source is less than the resonance frequency of

the cavity and negative if the source frequency is greater than

the resonance frequency of the cavity. When the primary loop is

closed, this output forces the frequency of the source in the

direction which minimizes the difference between the source

frequency and the cavity resonance frequency.

The secondary lock loop acts in the same manner as the primary lock loop. The output of the dc amplifier is fed into the

remote sensing terminals of the power supply. This causes a change in the output voltage of the supply. The frequency of

3
the microwave source is sensitive to the power supply voltage

and thus the loop acts to minimize the difference between the

source frequency and the microwave cavity frequency. This loop

greatly increases the locking range of the instrument and

effectively increases the lock accuracy by adding more gain to

the loop. A much slower time constant, on the order of two

seconds, is incorporated into the secondary loop to insure that

the two loops will be stable.

A schematic diagram of the lock loops is shown in Figure 4

The local oscillator is common to both lock circuits. Each

microwave oscillator has a low frequency output port whose

signal frequency is one seventh that of its high frequency

output. The two low frequency outputs are fed into a balanced

mixer circuit. The frequency of the output signal from the

mixer is equal to the difference in frequency between its two

inputs. This signal is fed directly to a commercial frequency

counter. The least significant digit of the counter represents

a 10 Hz signal. Thus each count on the counter signifies a frequency difference of 70 Hz.

4. Temperature Control Circuitry

The microwave hygrometer contains three oven control

circuits and one temperature monitor circuit. Each temperature

control consists of a coil of nichrome wire and electronic

circuitry which controls the amount of time which ac line

voltage is applied across the coil of wire. The circuits are

ze r o- c r os s i ng proportional temperature controls. When the oven

temperature is far below the setpoint temperature, the heater is

turned on all the time. As the oven temperature approaches the

setpoint, the heater is turned on for a proportionately smaller

part of the time and if the oven temperature exceeds the

setpoint by some amount, the heater is turned off all the time.

The power input to each heater is chosen so that the heater will

be on about half the time when the oven is at the setpoint

temperature. The circuitry will turn the heater on and off only

at the zero crossing points of the ac line voltage. This

minimizes the electrical noise generated by the heaters. The

circuits each consist of a thermistor bridge circuit whose

output is proportional to the difference between the temperature

of the thermistor and a setpoint temperature. The setpoint is

controlled by a variable resistor in one leg of the bridge. A

block diagram of one of the temperature control circuits is

shown in Figure 5. The output of the bridge circuit is buffered

and amplified by a dc amplifier and fed to one side of a comparator. This signal is a large positive voltage if the oven

temperature is below the setpoint and a large negative voltage

if the oven temperature is above the setpoint. As the oven

temperature approaches the setpoint, the signal will be in the

range between zero and minus one volt. This is the proportional

4
leg lull U L f h p con t rn 1 1 er . The o t h er input to t h e c om p a r a t o r i s

r> « rr o f" t \7 3. ucgd L1V e i 11 g

ramn J. U 111 U/ VV OW 1J- tt. 30U ^ e wh i c h starts at e r o and falls

l inea r iy i n u s one volt in a b o u t 2 D 0 ms . I t h en r e t u r n s r ap iu iy l ro . The output o f t h e comnarator 3 open c i r c u i ted

t t h o n p \7 p T" fLUCHp ramp voltage is m ore positive tha n th e b u f f e r ed

signal fr om t he thermi stor br

dge and it is a 1 o w im p e dance p a th

to ground whe nev e r the signal from the bridge i s m ore po s i t iv e than the ramp vol tage.

Th e output of the com p a r a t o r is o ne input to the optoi so la to r . An o pen c i r c ui t turn s 0 ff t he o p t o- iso 1 a t o r and a ground t urns it o n . Th u s , when th e o v e n i s m u ch c o 1 d e r than the

s e t po in t , t h e o p to- iso 1 a t o r is t ur ned o n all t he t ime and whe n the ove n is muc ll wa rm e r th an t h e s e tpo int the opt o -iso lator i s turned off all the time. When the temperature of the oven

approaches the setpoint, the o p t o - i s o 1 a t o r is turned on for that

portion of the time when the signal from the thermistor bridge

is more negative than the ramp voltage. The other input to the

op to- iso lator is a pulse from the zero crossing detector. The

input to this circuit is a 60 Hz sinewave which is in phase with

the line. This signal is full-wave rectified and sent to a circuit which puts out a +15 volt pulse whenever the ac line

approaches a zero cro ssing

a pu Is e o c c ur s f o r eac h half period

of the 60 Hz sinewave The ou t p ut of the o P t o- iso la tor i s a pulse, syncronized wi th the zero c r o s sings o f t he ac line , which

occurs whenever the s ignal from th e rm i s to r b r id ge is more

positive than the ram p volt age

E a c h pulse t ur n s o n a t r i ac for

one half period of th e line volt ag e . When t h e tr i ac is t ur ned

on, current flows thr o ug h a heat e r el em e n t i n t he 0 V en .

A s c hema t ic d i ag r am of the tempe r a t ur e c on t r 0 1 c ir cu its for

the inner oven, out e r oven and s am p 1

air h e a t e r i s shown in

Figure 6A s c h em a tic d i ag ram of the zero c r OS s i ng de tec tor,

ramp gene rato r and t emp e r a t ur e moni to r is s ho wn i n Figure 7 . The tempe rature mon i t o r c i r cult is id e n t i c al t 0 t h e front end of

a temperature control circuit, but the output of the buffer

amplifier is fed to a zero-center mic roamme ter . One division of

the meter corresponds to approximately 0.06°C. This meter

indicates when the inner oven temperature has reached the

setpoint.

5
5. Operation

Before the hygrometer is in an operative condition, the

cavities must be in temperature equilibrium and the REFERENCE

CAVITY must be dry.

5.1 Temperature Controls

It takes approximately 6 to 8 hours for the cavities to

reach a temperature equilibrium of 60°C. The TEMPERATURE MONITOR

METER, Figure 8, indicates the, cavity air bath temperature (inner

oven temperature). The meter is set so that the center position

(0 reading) corresponds to a temperature of 60°C. The inner

oven temperature controls should maintain a temperature of 60°

+ .03°C which corresponds to approximately + 1/2 division from

the setpoint on the TEMPERATURE MONITOR METER.

Step (1). Turn on power switch and set second switch to "Standby"

position, Figure 9. These switches turn on the inner oven heater,

outer oven heater, and blowers. In the "Standby" position the

vacuum pump and the sample air preheater are off.

5.2 Cavity Drying

It takes approximately 30 minutes to dry the cavities.

Step (1). a). Lay one layer of Teflon filter in the bottom

of the dryer jar.

b) . Fill the SAMPLE AIR DRYER with 2 pounds of

indicating CaSO (Drierite) and add 1/2 pound

of anhydrous Mg^(ClO,)_ on top of the CaSO..

4 2 4

c) . Lay one layer of Teflon filter on top of the

Mg (C10

4

) 2

.

d) . Fill 1/2 of the REFERENCE CAVITY DRYER U TUBE

with CaSO and 1/2 with Mg (CIO,),.

4 4 2 e) . Connect the SAMPLE AIR DRYER to the INLET VALVE.

f) . Connect the CaSO, side of the REFERENCE CAVITY DRYER

to the REFERENCE CAVITY FLOW RESTRICTOR line and the

Mg (C10,)„ side to the line labeled REF.

4 2 Step (2). Open the INLET VALVE and the inlet to the SAMPLE AIR

DRYER (rubber stopper).

Step (3). Open full (approximately 9 revolutions counterclockwise)

the REFERENCE CAVITY FLOW RESTRICTOR valve (micrometer

valve)

6
Step (4). Turn the switch from "Standby" position to "Operate"

position.

Step (5), Adjust the FLOW CONTROL VALVE (needle valve) located

in the VACUUM PUMP line so that the CAVITY PRESSURE

GAGE reads -1.3.

Renew the dessicants in the dryer when 3/4 of the indicating CaSO

turns pink.

5.3 Zero Reading

After the cavities are in temperature equilibrium and dry,

the reading on the COUNTER should be constant to + 1 count over

a period of 15 minutes. The ZERO READING is the reading on the

COUNTER when both cavities are dry. The ZERO READING must be

subtracted from all subsequent readings (readings taken with moist

air in the sample cavity).

ZERO READING should be taken at the beginning and the end of

each day of operation.

After taking the ZERO READING:

Step (1). Put switch in "Standby" position.

Step (2). Remove the SAMPLE AIR DRYER and seal the dryer

with rubber stoppers.

Step (3). Close the REFERENCE CAVITY FLOW RE STRICTOR valve

and then open the RESTRICTOR 7 revolutions

counterclockwise.

5.4 Sample Gas Measurements

The sample gas measurements are made after completing the

operations outlined in Paragraphs 5.1, 5.2, and 5.3. Before

proceeding to Step (1) check to see that: the INLET VALVE is open

and the REFERENCE CAVITY FLOW RESTRICTOR is adjusted to 7 revolutions

open from the closed position.

Step (1). Connect the sample air line to the INLET VALVE.

The sample air line should be 1/2" diameter tubing

to minimize the pressure drop in the line.

Step (2) Connect the AIR FILTER to the inlet of the sample

air line.

Step (3). Put switch in "Operate" position which turns on

the VACUUM PUMP and adjust the FLOW CONTROLLER

7
VALVE so that the CAVITY PRESSURE CAGE reads

-1.3. The nominal flow is now

adjusted for 10 1pm sample air and 0.1 1pm

dry air through the REFERENCE CAVITY.

After the TEMPERATURE MONITOR METER reading and the COUNTER

reading stabilize, s ub t rac t the ZERO reading from the COUNTER

reading. This value is the DELTA R listed in column 1 of Table 1.

Linear interpolation between the values listed in Table 1 is

better than + .01 C for Delta R between 37000 and 45 and + 0.1 C for

Delta R between 45 and 15.

5.5 Summary of Operating Procedure

Step (1). Turn the second switch to "Standby" position.

Step (2). Turn £n_ the Power switch.

Step (3). Connect the SAMPLE AIR DRYER to the sample air line.

Step (4). Connect the REFERENCE CAVITY DRYER.

Step (5). Open the SAMPLE AIR INLET valve after the cavities

reach temperature equilibrium (60°C) and open SAMPLE

AIR DRYER inlet (remove rubber stopper).

Step (6). Open full (turn counterclockwise approximately 9

revolutions from closed position) the REFERENCE CAVITY

FLOW RESTR ICTOR valve (micrometer valve).

Step (7). Switch to "Operate" position which turns on the VACUUM

PUMP and PREHEATER.

Step (8). Adjust the FLOW CONTROL valve (needle valve located

upstream of the VACUUM PUMP) so that the CAVITY

PRESSURE CAGE reads -1.3.

Step (9). ZERO READING. After the TEMPERATURE MONITOR METER

reads steady + 1/2 division from set-point (0 reading)

and the COUNTER reading reaches a constant value (+ 1 digit), record the COUNTER reading.

Step (10). Turn switch to "Standby" position.

Step (11). Disconnect the SAMPLE AIR DRYER.

Step (12). Close the REFERENCE CAVITY FLOW RESTRICTOR valve and

then open the RESTRICTOR valve 7 revolutions from

the closed position.

8
Step (13). Connect the sample air line (1/2" diameter tubing) to

the INLET valve.

Step (14). Connect the SAMPLE AIR FILTER to the inlet line.

Step (15). Turn on the VACUUM PUMP by switching to "Operate"

position.

Step (16). Adjust the FLOW CONTROL valve so that the CAVITY

PRESSURE GAGE reads -1.3.

Step (17). Record the COUNTER reading after the TEMPERATURE

MONITOR METER and the COUNTER readings reach stable

values .

Step (18). Subtract the ZERO reading (Step 9) from the COUNTER

reading (Step 17). This reading is listed as DELTA

R in Table 1.

Step (19). Enter DELTA R in Table 1 and obtain the corresponding

dew or frost point.

Take ZERO READING after completion of tests.

Step (20). Shut off the VACUUM PUMP by turning the switch to

"St andby" position.

Step (21) . Disconnect the sample air line at the INLET valve

and connect the SAMPLE AIR DRYER and open the inlet

to the DRYER.

SteD (22). Open full the REFERENCE CAVITY FLOW RESTRICTOR valve.

Step (23). Turn o_n the VACUUM PUMP by turning switch to "Operate"

position.

Step (24). Adjust the FLOW CONTROL valve so that the CAVITY

PRESSURE GAGE reads -1.3. Take ZERO READING.

Step (25). If the reading taken in Step (24) is different from

the reading taken in Step (9) use the average of the

two readings as the ZERO READING.

Step (26). Turn switch to "Standby".

Step (27). Shut off the INLET valve and the inlet to the SAMPLE

AIR Dryer.

Step (28). If the hygrometer is not going to be used within the

next 3 or 4 days, turn off the power switch. If the

hygrometer is going to be used within the next 3 or

4 days leave the power switch o n and the second switch

9
on "Standby". Start from Step 5 when the run is resumed

Replace either or both air driers when 2/3 of the indicating CaSO^ (Drierite) turns pink.

6 . Ca 1 ib ra t ion

The Microwave Hygromete^ was calibrated against the NBS twopressure humidity generator. ' Stability tests were performed by

making a number of calibrations over a span of six months. The

maximum uncertainty of the humidity generator is + Q.1°C for dew

points 40°C to -30 C, + 0.2°C for dew points -30°C to -45°C and

+ 0.5°C for dew points -45°C to -55°C.

6.1 Dew Point Calibration

The following second order equations for dew-point

temperatures as a function of Delta R (wet sample air reading

minus dry sample air reading) were obtained by means of least

squares regression fits to the data:

(a) . Fo r dew points (t) 40°C to 20°C ;

t = -32. 660598 - 11.228511 X + 5.9287645 X

2

(b) . Fo r dew points (t) 20°C to 0°C;

t = -51. 9 9 817 0 - 1.6250835 X + 4.7354931 X

2

(c) . Fo r dew points ( t ) 0°C to - 20°C ;

t = -60 . 658552 + 2 . 7393976 X + 4 . 1946508 X

2

(d) . Fo r dew points (t) -20°C to -40°C;

t = -7 1. 327487 + 9.0693096 X + 3.2985550 X

2

(e) . Fo r . frost points (t) 0°C to -27°C:

t = -67 . 698365 + 10.861096 X + 2.4453468 X

2

4

Wexler, A. and R. D. Daniels, Jr., "Pressure Humidity Apparatus",

J. Res. Nat'l. Bur. Std. 4_8 , 269 , ( 1952).

^Wexler, A., "Calibration of Humidity Measuring Instruments at the

Nat'l. Bur. Std.", Trans. ISA 7_» ( 1968) p. 356 .

10
(f). For frost points (t) -27°C to -53°C;

t = -73.687587 + 15.784185 X + 1.4101825 X

2

where X = log 1Q AR.

AR = moist air reading minus dry air reading.

The results of the above equations are given in Table 1.

Linear interpolation between the values listed in Table 1 is

better than +0.01°C for Delta R between 37000 and 45 and +0.1°C

for Delta R between 45 and 15.

As an estimate of the expected random error, the residual

standard deviations were calculated for the differences between

the calculated dew or frost points using the second order

equations and the generated dew or frost points of the two pressure

generator. The following estimates of the one sigma random error were

ob tained :

a) . 0. 02°C for dew points 40°C to +20° C

b) . 0. 03°C for d ew points 20°C to 0°C

c) . 0. 06°C for dew points 0°C t o -20°C

d) . 0. 43°C for d ew points -20°C to -40 °c

e) . 0. 09°C for f ros t points 0 C to -27 °c

f ) . 0. 60°C for f r os t points -27 °C to - 5 3°C

6.2 Vapor Pressure Calibration

The following third order equation for vapor pressure (Pascal)

as a function of Delta R (wet sample air reading minus dry sample

air reading) was obtained by means of least squares regression fit to

the data

e (Pascal) = -0.85096359 + 0.19764142 AR - 0.56181361 x 10" 7 (AR) 2 + 0.11756679 x 10" 11 (AR) 3

, where Pascal X 0.01 = millibar.

The above equation is tabulated in Table 2.

Again as an estimate of the expected random error, the

residual standard deviation was calculated for the differences

between the calculated vapor pressure using the third order

equation and the vapor pressure generated by the two pressure

generator. For Delta R between 15 and 37000 the estimate of the

one sigma random error was 2.25 Pa (.0225 mb) . This value of

11
one sigma random error corresponds very closely to an

uncertainty in the Delta R reading of + 11 units.

To convert the vapor pressure given by the above third

order equation to dew point temperature using the saturation

vapor pressure tables by Goff , the vapor pressure obtained by

the third order equation must first be divided by either f or

given in Tables 89 and 90 by List .

6

Goff, J. A., "Saturation Pressure of Water on the New Kelvin

Scale", HUMIDITY AND MOISTURE 3, Arnold Wexler (ed), Reinhold

Corp., N. Y . , 1965 p. 289 .

7 List, R. J., SMITHSONIAN METEOROLOGICAL TABLES, Smithsonian

Institution, Washington, D. C. 1951, p. 340.

USC OMM-N11S OC 12
Figure 1 Block diagram of the air sampling system.








Flpure 10. Interior view of the oven compartraent of MRS microwave

hydrometer, Model III.


Output Connector Pin Assignments

Function Counter Pin Wire Color Cannon

(Lower Plug) (pairs

Connector

1 6 Black H

2 H Red J

7 Black K

8 P White L

10 J Black M

20 L Green N

HO K Black P

80 9 Blue R

100 10 Black S

200 13 Brown T

400 12 Black U

800 11 Yellow V

IK N Black w

2K 15 Orange X

4K S Red Y

8K R Green z 10K 17 Red a 20K V White b

40K U Red c 80K T BLUE d

BCD Inhibit E Red

Transfer P Yellow f

Over fl ow 21— — Red

BCD Enable 22 Brown h

(Upper Plug)

Measure Enable Red i

Transfer Enable 6 Orange k

Conversion Period 11 Green 1

Blue

TABLE 1. MICROWAVE DEW-POINT ANT) FROST-POINT

DELTA DEW DELTA DEW

R DEG . C R

T"\ T- rt ,rt DEG • C

37000 OA "7 "7 39.77 O A A A A

3 2000 O O; A A 37.09

O t A A A 36900 OA lO 39.72 31900 37 . 03

O /f O A A 36800 39. 67 31800 O £ AT 36. 97

36700 Art /" rt 39. 62 Oil AA 31700 O £ A1 36. 91

*>//" rt A 36600 OA P O 39.57 O i /" AA 31600 36.86

36500 39.52 O T r rt rt 31500 36.80

36400 39.46 31400 36.74

36300 39.41 313 00 36.68

/* O rt rt 36200 OA O /* 39.36 O 1 O A A 31200 36.62

36100 39.31 31100 36.56

36000 39.26 31000 36.51

35900 39.21 O A A A A 30900 o /* / r 36.45

35800 39.16 O A A rt rt 30800 36.39

35700 39.10 30700 36.33

35600 39.05 30600 36.27

35500 39.00 3 0500 36.21

35400 38.95 30400 36.15

35300 38.89 30300 36.09

35200 38.84 O rt rt rt rt 3 0200 3 6 . 03

35100 38.79 30100 35.97

35000 38.74 O rt rt rt rt 30000 35. 91

O / A A A 34900 38. 68 O rt rt rt rt 29900 or or 35.85

34800 AO /" O 38. 63 A A O rt rt 29800 or O rt 35.79

A / T A A 34700 on r o 38.58 A AO rt rt 29700 or "i o 35.73

'Sit. AA 34600 on r o 38.52 A A f rt A 29600 or /* /* 35.66

34500 38.47 29500 35.60

34400 38.42 29400 35.54

34300 38 .36 rt rt ^ s\ a 293 00 35.48

34200 38.31 rt rt rt rt 29200 35.42

# "1 Art 34100 38.25 29100 35.36

o / A A rt 34000 38.20 rt rt rt rt rt 29000 35.29

o >*i rt rt rt 33900 38.15 rt rt r\ f\ r~\ 28900 35.23

33800 38.09 28800 ' 35.17

33700 38.04 28700 35.10

33600 37.98 28600 35.04

33500 37 .93 28500 34.98

33400 37 .87 28400 34. 91

O rt rt rt rt 33300 37.82 283 00 34.85

o o rt rt rt 33200 37.76 rt rt *^ /*\ rt 28200 34.79

33100 37 .71 28100 34 .72

33000 37.65 28000 34.66

32900 37.59 27900 34.59

32800 37.54 27800 34 .53

32700 37.48 27700 34.46

32600 37.43 27600 34.40

32500 37.37 27500 34.33

32400 37.31 27400 34.27

rt rt rt ^ r\ 32300 37.26 27300 34.20

32200 37.20 27200 34.14

32100 37.14 27100 34.07
TABLE 1. MICROWAVE DEW-POINT AND FROST-POINT

DELTA DEW DELTA DEW

R DEG. C R DEG. C

27000 34.00 22000 30.38

26900 33.94 21900 30.30

26800 33.87 21800 30.22

26700 33.80 21700 3 0.14

26600 33.74 21600 30.06

26500 33.67 21500 29.98

26400 33.60 21400 29.89

26300 33.53 21300 29.81

26200 33.47 21200 29.73

26100 33.40 21100 29.65

26000 33.33 21000 29.57

25900 33.26 20900 29.48

25800 33.19 20800 29.40

25700 33.12 20700 29.32

25600 33.05 20600 29.23

25500 32.98 20500 29.15

25400 32.91 20400 29.06

25300 3 2.84 20300 28.98

25200 32.77 20200 28.89

25100 32.70 20100 28.81

25000 32.63 20000 28.72

24900 32.56 19900 28.63

24800 32.49 19800 28.55

24700 32.42 19700 28.46

24600 32.34 19600 28.37

24500 32.27 19500 28.28

24400 32.20 19400 28.20

24300 32.13 19300 28.11

24200 32.05 19200 28.02

24100 31.98 19100 27.93

24000 31.91 19000 27.84

23900 31.83 18900 27.75

23800 31.76 18800 27.66

23700 31. 6S 18700 27.56

23600 31.61 18600 27.47

23500 31.54 18500 27.38

23400 31.46 18400 27.29

23300 31. 3S 18300 27.20

23200 31.31 18200 27.10

23100 31.23 18100 27.01

23 000 31.16 18000 26.91

22900 31.08 17900 26.82

22800 31.00 17800 26.72

22700 30.93 17700 26.63

22600 30.85 17600 26.53

22500 30.77 17500 26.43

22400 30.69 17400 26.34

22300 30.61 17300 26.24

22200 30.54 17200 26.14

22100 30.46 17100 26.04
TABLE 1

DELTA DEW

R DEG . C

17000 at a / 2d . 94

16900 2d. 84

16300 *i C a* / 25 .74

16700 AC £ / 25 . 64

16600 a c r / 2d . 54

16500 25.44

16400 25 .34

16300 25.23

16200 25 . 13

16100 25 . 03

16000 24 . 92

15900 24.82

15800 24 .71

15700 24 . 60

15600 24 .50

15500 24.3 9 15400 24 .28

15300 24 .17

15200 24.06

15100 23 . 95

15000 23 .84

14900 a a a* a 23 .73

14800 23 . 62

14700 23 .51

T / £ rt A 14600 a a / r\ 23 . 40

14500 23 .28

14400 23.17

14300 23 . 05

14200 22. 94

14100 22.82

14000 22.70

13900 22 .58

13800 22.47

13700 22.3 5

13600 22.23

13500 22.10

13400 21. 98

13300 21.86

13200 21. 74

13100 21.61

13 000 21.49

12900 21.3 6

12800 21.23

12700 21.11

12600 20. 98

12500 20.85

12400 20.72

12300 20.59

12200 20.46

12100 20.32

MICROWAVE DEW-rOINT AND FROST-POINT

DELTA DEW

R DEG , C

i o a a a

1 ZUUU A A 1 A 20.19

iiy uu

A A AC 20 . 05

T T O AA 118 00 19.90

t i "7 aa 117 00 1 A A /" 19.76

11600 1 A /"A 19. 63

115 00 1 A / A 19.49

T T / AA 11400 19 .35

1 T A A-A 113 00 " 19.21

t t a a a 11200 19 . 07 - 11100 18 .92

11000 18 . 78

1 A A A A 10900 i A r a 18 . 63

T AO AA 108 00 18.49

1 A^ AA 107 00 TO A / 18 .3 4

1 A £ AA 10600 TO 1 A 18 .19

1 A C AA 10500 TO A / 18 . 04

1 A / A A 104 00 17 .89

T AA A A 103 00 ^ A AT J 17.74

T AA AA 10200 17 .53

1 AT A A 10100 T A /A 1/ .43

T A A A A 10000 T A A A 17 . 27

A A A A 9900 T A T T 17 . 11

A 0 AA 98 00 T C AC 16 .95

A "7 A A 9700 16.79

A /" AA 9600 16.63

A C A A 9500 16.46

r\ I a A 9400 16 .30

A A A A 9300 16.13

A A AA 9200 15. 96

A 1 A A 9100 15. 79

A A A A 9000 1 P /"A 15 . 62

O A A A

8 900 15.45

O O AA 88 00 T C A A 15.27

O A* A A 8700 15. 09

8600 14. 91

A r A A 8500 14.73

8400 14 .55

8300 14.37

A A AlA 8200 *1 / TO 14 .18

8100 13. 99

n A A_A 8000 13 .80

i AA A

7 900 13 . 61

A A AA 78 00 ^ A /I 13 .41

A1 A1 A A 7700 13. 21

7600 13 .02

A1 C A A 7500 12.81

^ / AA 74 00 T A /* 1 12 . 61

7300 12. 40

7200 12.19

7100 11.98
TAUT P 1. MILKUWWE DEW-POINT AND FROST-•POINT

DELTA DEW DELTA DEW FROST

R DEC C R DEG. C DEG. C

7aaa / uuu 1 1 77 11. / / 1 AQ A JOoU — AC . 05 — AC . 05

conn oyuu 1 1 CC 11* 55 1 ACA JUbO — 1 /. . 14 — 1 0

. U

OOUU 11 ii 11* J J

"J AA A JU4U —. ZJ — 01

. 21

C7 aa O/UU ii ii 11. 11 1 AO A JUZU 1

—.J J — 00 .zy

ccaa ObUU 1 A OQ 10. OO 1 AAA J UUU — /. 7 . 4Z — 07 . j/

b5U0 1 A £ C 10. 65 zyou 0 OQ A — CI. 51 — /. c .45

c a aa b400 i a / o 10.42 /you 7GCA — CA . 0U , — CO . 5J

CO Art bJOO 1 A "1 O 10. lo zy4u — 7 A . /U _— CI . 01 co aa OZOU O DC

y . y5 zyzu 7Q7 A in —. / y — CO . oy

blOO O 1 A 9.70 OOAA zyuu — QO . oy — 7Q . /O

C AAA bOOO O A £ 9.46 ZOoU 7P.Q A — QQ . yo —• 00QC

c oaa ->yuu

n9.21n OQ Cn zoou —11 AQ . Uo — OC . y5

CQ AA 5o00 O A£96 OQ/. A Z04U —1 1 Q 1. lo —11 AO . UJ

C7 AA O T A o.70 OQO A ZoZU 1 0*7 —l.Z/ —1.11 1 11

£ C AA JOOO Q A /. 0.44 OOAA zouu —1.1 "3 7 J / —11 7 A • ZU

C CAA 5500 O .17 07QA Z /OU —1.4/ 1 1.1 —11 O Q . zy

c /. nn 5400 7. 91 07C A z/ou —1.5/ 1 C7 —1i 07 . j / conn 5300 7.63 O 7 A A —11 C7 .0/ —1.4 1 /. c0

CO AA 5200 7.35 O "70 A z/zu —1 7 7 1. / / —1.55 1 c c CI AA 5100 7 .07 O "f AA z/oo 1 Q7 —l»o/ —11 c/.

. 04

C AAA 50U0 D. /O ZboO 1 07 -1. y/ —11 7 0

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/i Q AA C AO b.4y OCCn ZOOO O A7 —z . u/ —11 Q 0

. oZ

/• Q A A 40UU £ 1 0 b.iy Z04U OA/. A 0 1 Q —Z. lo —11 OI • yi

/• 7 AA 4 / UU C Q O 5. yy OCO A ZOZO —0 OQ / . Zo 0 AA —z . uo

/. Cnn 4bUU C CO 5.5o 0 inn ZOOO 0 1Q —z . j y7 AO —z . uy

/. C AA 4500 C O c 5. 26 O CO A Z5o0 O AO -z . 4y O 1 Q —Z . lo

44UU A AAA A OA 4 • y4 O CC A Z5o0 O 'CA —Z • oU O O Q —Z .Zo

A O AA

4J 00 A £ O 4. 62 O CA A Z540 O 7 A —Z. /O 0 07 —Z.J/

4ZUU / O A A A OO 4.Zo O CO A Z5Z0 O Q

—Z . ol 0 /. c —Z .40

/ 1 AA Hi 00 3 . 94 0 cnn Z500 O QO —z. yz 0 c c —Z .5b

/. AAA 4000 O C A 3.59 0 A q n Z4o0 O AO -J . UJ 0 c c —Z * b5

O QAA j yoo 3 .23 0/. c n Z4b0 0 1 /. -J . 14 O 7 c —Z . / 5

O O AA JoOO 0 0 1 2.87 0 /. a n Z44U 0 0 c —J . Z5 O Q C —Z . o5

3/00 2.50 0/. 0 n Z4Z0 —J.JO 0 oc —z. y5

o £ a a JoOO O IT* 2.11 0Z400 /. nn 7. /. 7 —J . 4 / 0 AC —J . UD 3500 1.72 01 on ZJoO 0 C Q —J • 5o O 1 A —J . 14

o ma J A 00 1 .32 ZJOO a 7 a —J . / U

0 0 c —J .ZD

o *"> a a 3300 . 91 00/. n ZJ40 0 Q

—J .Oi 0 0 c —J . J5

1 O AA 3200 .49 O O O A 2320 —O OO j . yj O AC —J .45

O 1 A A 3100 .05 O O AA 2300 —A A/ 4 . 04 0 c c —J . 55

00 on ZZoO -4.1b 0 cc —J . b5

O O £ A 2260 A O O -4 .Zo O 7C —J . /b

O O / A 2240 a / n —4.40 0 0 c —J . ob

ooon" ZZZO —A CO 4 ,5Z o 07 —j . y/

OOAA 2200 / CI. -4 . 64 —4. Oo

O 1 O A 2180 -4.7 6

A IO -4. lo

oi en Z10U A Q A —4 .oy —

A O O 4 . zy

O 1 A A Z140 C A1 —5 . 01 A A A —4 . 40

O 1 O A Z1Z0 c 10 -5 . 13 A CI -4. 51

2100 -5.26 -4.63
DELTA

R

TABLE

DEW

DEC. C

1. MICROWAVE DEW-POINT AND FROST-POINT

FROST DELTA DEW FROST

DEC. C R DEC. C DEC C

2080 -5.39 -4.74

2060 -5.52 -4.85

2040 -5.65 -4. 97

2020 -5.78 -5.08

2000 -5.91 -5.20

1980 -6.04 -5.32

1960 -6.17 -5.44

1940 -6.31 -5. 56

1920 -6.45 -5.68

1900 -6.58 -5.80

1880 -6.72 -5.92

1860 -6.86 -6,05

1840 -7.00 -6.17

1820 -7.15 -6.30

1800 -7.29 -6.43

1780 -7.44 -6.56

1760 -7.58 -6.69

1740 -7.73 -6.82

1720 -7.88 -6.96

1700 -8.03 -7.09

1680 -8.19 -7.23

1660 -8.34 -7.37

1640 -8.50 -7.51

1620 -8.66 -7.65

1600 -8.82 -7.79

1580 -8.98 -7.94

1560 -9.14 -8.08

1540 -9.31 -8.23

1520 -9.48 -8.38

1500 -9.64 -8.53

1480 -9.82 -8.69

1460 -9.99 -8.84

1440 -10.16 -9.00

1420 -10.34 -9.16

1400 -10.52 -9.32

1380 -10.70 -9.49

1360 -10.89 -9.65

1340 -11.07 * -9.82

1320 -11.26 -9.99

1300 -11.45 -10.17

1280 -11.65 -10.34

1260 -11.85 -10.52

1240 -12.04 -10.70

1220 -12.25 -10.88

1200 -12.45 -11.07

1180 -12,66 -11.26

1160 -12.87 -11.45

1140 -13.09 -11.65

1120 -13.30 -11.84

1100 -13.53 -12.05

1080 -13.75 -12.25

1060 -13 . 98 -12.46

1040 -14.21 -12.67

1020 -14.45 -12.89

1000 -14.69 -13.11

980 -14 . 93 -13.33

960 -15.18 -13 . 56

940 -15.44 -13 .79

920 -15.69 -14 . 03

900 -15.96 -14.27

880 -16.22 -14 . 52

860 -16.50 -14.77

840 -16.78 -15.03

820 -17.06 -15.29

800 -17.35 -15.56

780 -17.65 -15.83

760 -17.96 -16.12

740 -18.27 -16.40

720 -18.58 -16.70

700 -18.91 -17.00

680 -19.25 -17.31

660 -19.59 -17 .63

640 -19. 94 -17 . 96

620 -20.30 -18 .30

600 -20.67 .-13.65

590 -20.87 -18 . 83

580 -21.08 -19.01

570 -21.28 -19.19

560 -21.49 -19.38

550 -21.70 -19.57

540 -21.92 -19.76

530 -22.14 -19.96

520 -22.36 -20.16

510 -22.59 -20.36

500 -22.82 -20.57

490 -23 . 06 -20.73

480 -23.30 -21.00

470 -23 . 54 -21.22

460 -23.79 -21.44

450 -24.04 -21.67

440 -24.30 -21.90

430 -24.57 -22.14

420 -24.84 -22.38

410 -25.11 -22.63

400 -25.40 -22.88

390 -25.68 -23.14

380 -25.98 -23.40

370 -26.28 -23.68

360 -26.59 -23 . 95

350 -26.91 -24.24
TABLE 1. MICRO WWE DEW-POINT AND FROST-POINT

DELTA DEW FROST

R DEG. C DEG. C

340 -27 . 23 -24.53

330 -27.56 -24.83

320 -27.91 -25.14

310 -28.26 -25.46

300 -28.62 -25.79

290 -23.99 -26.13

280 -29.38 -26.48

270 -29.78 -26.84

260 -30.19 -27.34

250 -30.61 -27.73

240 -31.05 -28.13

230 -31.51 -28.54

220 -31.98 -28.98

210 -32.48 -29.43

200 -32.99 -29.90

190 -33.53 -30.40

180 -34.10 -30.92

170 -34.69 -31.47

160 -35.31 -32.05

150 -35.97 -32.66

140 -3 6.67 -33.32

130 -37.42 -34.02

120 -38.21 -34.77

110 -39.07 -35.59

100 -3 9.99 -36.48

90 -37.46

85 -37.98

80 -38.54

75 -3 9.13

70 -39.76

65 -40.44

60 -41.16

55 -41.95

50 -42.80

45 -43.74

40 -44.78

35 -45.95

30 -47.30

25 -48.87

20 -50.76

15 -53.17
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Q 1 5J /b .ol 990 nn ZZ J UU

AO 0 1 AC 4J yi . b5

9. 9 9 AA JZZUU £7/,/ OA bJ44 . Z0 7 7 o nn Z 7Z 00 c 0 C7 no 5J 5/ . oy 0 9 9 nn ZZZUU

AO 7 1 OA 4J / 1 . y b 1 0 1 A A JZ1UU £ o O A / / bJZ4 ,44 o7i nn 27100 C 7 7 7 7 7 5J J7 . J 7 22100 4352.27
TABLE 2. MICR0V7AVE VAPOR PRESSURE

DELTA VAPOR DELTA VAPOR DELTA VAPOR

R PRESSURE, R PRESSURE, R PRESSURE,

PASCALS PASCALS PASCALS

22000 4332.59 17000 3348.59 12000 23 64.79

21900 4312.90 16900 3328.92 11900 2345.11

21800 4293.21 16800 3309.24 11800 2325.43

21700 4273.53 16700 3239.57 11700 2305.75

21*600 4253.84 16600 3269.89 11600 2286.06

21500 4234.15 16500 3250.22 11500 2266. 3S

21400 4214.47 16400 3230.54

' 11400 2246.70

21300 4194.78 16300 3210.87 11300 2227.02

21200 4175.10 16200 3191.19 11200 2207 .34

21100 4155.41 16100 3171.52 11100 2187.65

21000 413 5.73 16000 3151.84 11000 2167.97

20900 4116.05 15900 3132.17 10900 2148.29

20800 4096.36 15800 3112.50 10800 2123.60

20700 4076.68 15700 3092.82 10700 2108.92

20600 4057.00 15600 3073.15 10600 2039.24

20500 4037 . 32 15500 3053.47 10500 2069.55

20400 4017.63 15400 3 033 . 30 10400 2049.87

20300 3 997.95 15300 3 014.12 10300 2030.18

20200 3978.27 15200 2994.45 10200 2010.49

20100 3958.59 15100 2974.77 10100 1990.81

20000 3938.91 15000 2955.10 10000 1971.12

19900 3919.23 14900 2935.42 9950 1961.28

19800 3899.55 14800 2915.75 9900 1951.43

19700 3379.87 14700 2396.07 9G50 1941.59

19600 3860.19 14600 2876.40 9800 1931.75

19500 3840.51 14500 2856.72 9750 1921.90

19A00 3820.83 14400 283 7.05 9700 1912.06

19300 3801.15 14300 2817.37 9650 1902.21

19200 3781.47 14200 2797.70 9600 1892.37

19100 3761.80 14100 2778.02 9550 1832.52

19000 3742.12 14000 2758.34 9500 1372.68

18900 3722.44 13900 2738.67 9450 1862.84

18800 3702.76 13800 2718.99 9400 1852.99

18700 3683.09 13700 2699.31 93 50 1843.15

18600 3663.41 13600 2679.64 9300 1833.30

18500 3643.73 13500 2659.96 9250 1823 . 46

18400 3 624.05 * 13400 2 64 0.28 . 9200 1813.61

18300 3604.38 13300 2620.61 9150 13 03 . 77

18200 3584.70 13200 2600.93 9100 1793.92

18100 3565.02 13100 2581.25 9050 1784.07

18000 3545.35 13000 2561.58 9000 1774.23

17900 3525.67 12900 2541.90 8950 17 64.38

17S00 3 506.00. 12300 2522.22 8900 1754.54

17700 3436.32 12700 2502.54 8850 1744.69

17600 3466.64 12600 2482.06 8800 1734.64

17500 3446.97 12500 2463.18 8750 1725.00

17400 3427.29 12400 2443.51 8700 1715.15

17300 3407.62 12300 2423.83 8650 1705.30

17200 3387.94 12200 2404.15 8600 1695.46

17100 3363.27 12100 2334.47 8550 1635.61
TABLE 2. MICROWAVE VAPOR PRESSURE

DELTA VAPOR T\T"*T T* A DELTA VAPOR DELTA VAPOR

R PRESSURE, R PRESSURE, R PRESSURE,

PASCALS PASCALS PASCALS

8500 1675.76 6000 1183 .23 3500 690.26

8450 1665.92 r A r A 5950 1173 .37 3450 ' 680.39

8400 1656. 07 5900 1163 .52 3400 670.53

8350 1646.22 5850 1 1 C f £ 1153 .06 3350 660. 66

8300 1636.37 5800 11/1 O 1 1143 .81 3300 650.80

8250 1626.53 5750 1133 .95 3250 640. 93

8200 1616. 68 CT AA 5700 1 1 1 / 1 A 1124 .10 3200 631 . 06

8150 1606.83 5650 1114 .24 -3150 621.20

8100 1596. 93 5600 1 i / 1 r\ 1104 .3 9 3100 611.33

8050 15871.14 5550 1094 .53 3050 601.47

8000 1577.29 5500 1084.67 3000 591.60

7950 1567.44 5450 1074 .82 2950 581.73

7900 1557.59 5400 1064 .96 2900 571.87

7850 1547.74 5350 1055.10 2850 562.00

7800 1537.89 p»\ AA 5300 1045 .25 2800 552.13

7750 1528. 04 FIFO 5250 1035.3 9 2750 542.26

7700 1513.19 5200 1025.53 2700 532.39

7650 1508.34 5150 1015 .67 2650 522.53

7600 1498.49 5100 1005.81 ' 2600 512.66

7550 1488. 65 5050 995. 96 2550 502.7 9

7500 1478.80 5000 986.10 2500 492.92

7450 1468. 95 4950 976.24 2450 483 . 05

7400 1459.10 4900 966.38 2400 473 .18

7350 1449.25 4850 Af / r* o 956.52 2350 463.31

7300 1439.39 4800 946.66 2300 453 .44

7250 1429.54 4750 936. 80 2250 443 .57

7200 1419.69 4700 926.94 2200 433.70

7150 1409.84 4650 917. 09 2150 423 .83

7100 1399.99 4600 907 .23 2100 413 .96

7050 i r\ r\ i / 1390.14 4550 897.37 2050 404.09

7000 1330.29 4500 887 .50 2000 3 94.22

6950 1370.44 4450 877.64 . 1950 384.34

6900 13 60.59 4400 867 .78 1900 374.47

6850 1350. 73 4350 857. 92 1850 364.60

6800 1340.88 4300 848 .06 1800 3 54.73

6750 1331. 03 4250 838. 20 1750 344 .86

6700 1321.18 4200 828.34 1700 334.98

6650 1311.33 4150 818.48 1650 325.11

6600 1301.47 4100 8 08 . 6 2 1600 315.24

6550 1291. 62 4050 798.75 1550 3 05 . 3 6

6500 1281.77 4000 788.89 1500 295.49

6450 1271. 91 3950 77 9. 03 1450 235.61

6400 1262.06 3900 769.17 1400 275.74

6350 1252.21 3850 759.30 1350 265.87

6300 1242.35 3800 749.44 1300 255.99

6250 123 2.50 3750 73 9. 58 1250 246.12

6200 1222.65 3700 729.71 1200 236.24

6150 1212.79 3650 719.85 1150 226.36

6100 1202 .94 3 600 709.93 1100 216.49

6050 1193.08 3550 700.12 1050 206.61
TABLE 2. MICROWAVE VAPOR PRESSURE

DELTA VAPOR

R PRESSURE,

PASCALS

1000 196.74

950 186.86

900 176.98

850 167.10

800 157.23

750 147.35

700 137.47

650 127.59

600 117.71

550 107.84

500 97.96

450 88.08

400 78.20

350 68.32

300 58.44

250 48.56

200 38.68

150 28.79

100 18.91

80 14.96

60 11.01

40 7.05

20 3.10
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 75-7582. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Operational Manual for Microwave Hygrometer

Rff^J-^T "TXT Model III

5. Publication Date July 1975

6. Performing Organization Code

7. AUTHOR(S)Daniel p ^ stokesberry & Saburo Hasegawa 8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARD*/

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Naval Air Systems Command

Department of the Navy

Washington, D. C. 20360

13. Type of Report & Period Covered

Pinal

14» Sponsoring Agency C3ode

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This is an operational manual for the MRS microwave hygrometer,

Model III. It covers the design, operation and performance of the

hygrometer. It is capable of measuring water vapor equivalent to

the dew/frost point range of 40°C to -53°C.

When compared with the MBS two-pressure humidity generator over

the dew/frost point range of ^0°C to -53°C, the following estimates

of the one sigma random errors were obtained:

a) 0.02°C for dew points H0°C to 20°C

b) 0.03°C for dew points 20°C to 0°C

c) 0.09°C for frost points 0°C to -27°C

d) 0.60°C for frost points -27°C to -53°C

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Dew-point; hygrometer; microwave hygrometer

18. AVAILABILITY Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

|_Xl For Official Distribution. Do Not Release to NTIS

UNCLASSIFIED

Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C. 20402. SD Cat. No. CI 3

20. SECURITY CLASS

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22. Price

1 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED

USCOMM-DC 29042-P74