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national Bureau of standard

Jbrary E-01 Admin. B!dP OCT 6 1969

490

Thermal Gradient Effects

On Thirteen Flush Mounted

Pressure Transducers

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U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards
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UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

NBS TECHNICAL NOTE 490

ISSUED AUGUST 1969

Nat. Bur. Stand. (U.S.), Tech. Note 490, 23 pages (Aug. 1969)

CODEN: NBTNA

Thermal Gradient Effects on Thirteen

Flush Mounted Pressure Transducers

Leon Horn

Electronic Technology Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, Government Printing Office

Washington, D.C, 20402 - Price 30 cents
Contents

Page

1. Introduction 1

2. Test Equipment 2

3. Test Program 3

4. Test Results 3

5. Analysis 5

6. Effective Gradient Sensitivity 6

7. General Comments 6

8. Summary 7

List of Tables

Table 1: Oil Canning 9

Table 2: Thermal Gradient Response 10

Table 3: Effective Thermal Gradient 11

Table 4: Response To Thermal Gradients 13

List of Figures

Figure 1: Thermal Gradient Test System .14

Figure 1A: Gradient Heater 15

Figures 2 through 7: Thermal Gradient Response 16-21

li
Thermal Gradient Effects on Thirteen

Flush Mounted Pressure Transducers

Leon Horn

Thirteen different flush mounted pressure transducers of

seven manufacturers were tested by creating a thermal gradient

in them and recording the resultant zero shifts. Photographs

of typical outputs are shown and the results are compared. A

typical recording shows these general characteristics; 1. a very rapid change in output reaching a peak in a second or

less, 2. a more gradual shift which reaches a peak in a time

which may be a few seconds or more than a minute, and 3. a shift in reading which remains as long as the gradient is

maintained. Examples were found in which each of these were

positive or negative. The magnitude in a few cases was

small, in many was a large fraction of its range, and in one case well in excess of the full scale range.

KEY WORDS: Temperature, thermal gradients, pressure transducers, response, zero shift, pressure measurement errors.

1. Introduction

The effects of thermal gradients on the zero outputs of thirteen com- mercial pressure transducers have been studied. 1 Since the total number

of transducers studied is not sufficient for a statistical evaluation,

nor any segment large enough to be representative of a type of transducer

or of a particular manufacture's transducers, the results are only indicative of the range of performance that may be encountered. We have

studied transducers of similar design but of different manufacture as well as those of different design of the same manufacture.

To provide the user with a basis for judging whether a particular

pressure transducer will meet the requirement of his application, the

transducer manufacturer specifies the performance of the instrument over

a range of temperature in which valid results may be expected. Effects

of temperature on sensitivity and on zero-pressure response are usually

specified. In the majority of transducers a shift of the zero-pressure

response equal or less than 0.02% of full scale per degree Fahrenheit is

specified.

Customarily these specifications of temperature~range performance

of pressure transducers refer to equilibrium conditions, that is, to

conditions in which temperature is uniform throughout the transducer.

In standard temperature tests as recommended by the Instrument Society

Response of Flush Diaphragm Pressure Transducers to Thermal Gradients

Preprint No. 13,3-4-65 ISA 1965.
of America one waits for a constant temperature to be established within

the transducer before recording its output. Since equilibrium conditions

do not always exist at the time of measurement in many applications, the

validity of this type of temperature test alone to determine the temperature performance characteristics of pressure transducers is open to question. One can expect to find variations in temperature occurring during

the measurement process, often caused by the same process that produces

the pressure being measured.

A change in temperature can alter the output of a pressure transducer by changing its damping and thus its dynamic response; by altering

its sensitivity and thus its output; by altering its zero-pressure output

and thus the calibration base line. The study reported here investigated

the influence of thermal gradients on the zero response of pressure transducers as distinct from those of changes in uniform temperature. Conditions of observation were such that no part of the instrument was exposed

to a temperature greater than its proper operating range.

A word of caution should be noted. For instruments of the type

tested (the flush mounted diaphragm pressure transducer) one could be

dealing with the effects on the output due to: (1) A steady state

gradient through the instrument. This is encountered in high speed aircraft by instruments installed between the cooled interior and the

exterior which is heated by air friction; also by instruments installed

near the engines of conventional aircraft (the gradient can be in any

direction), or (2) A changing ambient temperature uniform in space; this,

because the various components of the instrument follow the temperature

change with different lags. In addition, even though an instrument has

been designed to cope with both of the above conditions it still has to

cope with changes with time in the gradient of temperature in the instrument, and or (3) Short term non-steady-state gradients in the environment. (Caused in many cases by the phenomena that is generating the

pressure being measured.) While these tests are specifically aimed at

conditions of temperature gradients in one particular direction, for

gradients in different directions one can expect comparable effects and

they should be investigated by the user.

2. Test Equipment

To evaluate the effects of thermal gradients on pressure transducers,

a device capable of establishing thermal gradients in flush mounted pressure transducers was built.

An electric soldering iron was altered to serve as the heat source

for generating gradients. Heat is transferred to the transducer by con- duction through the thermal contact of the converted iron with a pool of

molten Wood's metal. With the addition of an insulation shield and means

for measuring and controlling heat output, the converted iron was found

capable of transfer of 35 kW/m2 at (107°C) 225°F and 318 kW/m2 at (482°C)

900°F. During a run, the temperatures of all the major components of the
test are continuously monitored, and the thermal output of the heater can be altered by adjusting the input voltage to the heater.

Figure 1 shows the test assembly. The pressure transducer can be

seen at (A). It is held by an insulated clamp (B) . During the test its

surface is just immersed in the liquid Wood's metal pool (C) which is

used as heat transfer medium. The heater voltage is controlled by an adjustable autotrans former (D) . Thermocouples (E) are used to measure

the temperature of the Wood's metal and of the front and back surfaces of

the transducer. A recorder is used to keep multiple continuous records

of temperatures during the test. The electrical output of the transducer

is displayed on an oscilloscope and photographed.

3. Test Program

Each transducer was first checked using the standard series of uniform temperature tests 2 in order to compare its performance with that

listed in the manufacturer's specifications; all were found to be within

specifications

.

The gradient test produces a temperature gradient within the pressure

transducer with the high temperature region at the pressure sensing end.

In a typical test series the temperature of the heat source was increased

in steps, running one test at each step, until the specified limiting

operating temperature of the transducer was reached. The temperature of

the sensing end and the back of transducer and the zero level output were

recorded during each run.

The tests to date have been limited to a maximum front surface

temperature of 600°F (315. 5°C). A heat influx of approximately 225

kW/m2 was required to achieve this temperature.

4. Test Results

A typical thermal gradient zero shift curve from a flush diaphragm

type pressure transducer, Figure 2 (a), shows the following:

1. A very rapid change in output reaching a peak in a second or less (in this instance a negative peak value)

.

2. A more gradual shift which reaches a peak in a time which may

be a few seconds or more than a minute.

3. A shift in zero reading which tends to level off toward some value which may remain as long as the gradient is maintained.

In this instance the maximum zero shift was not in the same direction as the initial peak shift.

2 NBS Technical Note #411, February 9, 1967, Methods for PerformanceTesting of Electromechanical Pressure Transducer, P. S. Lederer.

3
The initial portion of the curve has been interpreted as "oil

canning," the differential expansion and "popping" of a diaphragm held by

a rigid hoop. In general, this is observed as a rapid response, i.e.,

"oil canning" can occur in less than one second. It varied from +2.0% FS

(full scale) to -30% FS and appeared to be least in those instruments

that showed the smallest zero shift.

Figures 2a and 2b show the effect of what is being called "oil

canning" in the output of two different transducers . Figure 2b shows an unusually large effect. It, and the maximum zero shift are closely re- lated in this instance and represent the largest response of the kind

observed. Figure 3a is included to show the possible response speed of

such behavior. For this transducer, a piezoelectric type, a change of

1.9% FS (in this instance, 332 kN/m2

) occurred in a fraction of a second.

The photographs of the shifts of the zero level outputs of the

various transducers have been given effective gradient numbers which

represent the transducer's position in the ordered sequence of effective

gradient sensitivities. The photographs represent typical zero-shifts

and were not chosen for maximum test conditions. The test temperature

is given alongside each photograph. It was noted that while duplicate

transducers tested (Figure 3, photographs (b) and (c) same model series

number and range) under duplicate conditions gave similar results, some units of the same manufacturer and same series but of different pressure

ranges did not. (Figure 4, photographs (a), (b) , and (c) are of the same model series but of different ranges.)

On all the transducers tested, as long as a gradient existed, a zero shift was observed and a zero shift steady state condition could be

approached. Photos, Figures 6a, 6b, and 6c, are particular examples

of this condition.

Excluding the initial pulse, a separation of the thirteen observations into two patterns can be noted. The division is between those

whose zero shift maximizes within the test period and those tending to

show a gradual increase with time (see remarks in Table 4) . Since maxima

were observed only in compensated transducers, it is suggested that

placement of the temperature compensating elements may be responsible,

The maximum zero shifts and response time of the different transducers are listed in Table 4. It was noted that an increase in the rate

of heating from 35 kW/m2 to 350 kW/m2 did not alter the time required to

reach maximum zero shift in the tests, although the increase did alter

the gradient and the magnitude of maximum zero shift.

A review of the data taken during all the tests indicated that the

gradient induced during a particular transducer test is related to the

temperature of the hot pool with which the transducer is in contact and

the length of time it has been immersed. The numerical value of the

maximum zero shift thus depends to a great extent of the test conditions.
where Z where M where A

where B and X

5. Analysis

An example of the analysis of one particular transducer involving

an intermediate rate of thermal gradient is as follows. The empirical

relationship, Z = A° • y + X.: (A° - B°) , was found to hold for the conditions over which flush mounted pressure transducers were tested.

= zero output as % FS,

= manufacturer's thermal coefficient per degree,

= temperature of front surface of the transducer,

= temperature of back exposed surface of the transducer,

= correction coefficient for the specific condition of

the test and particular transducer (j).

In order to find the numerical value of the correction coefficient X

for a particular pressure transducer, one makes a gradient temperature

run with the transducer held at a measured temperature A at the active

front surface, and records the temperature B of the exposed back surface

and the zero pressure level output of the transducer. The Values of A,B

and the manufacturer's specification for zero output as a function of

operating temperature is then used in the equation. One solves for X.

One assumes that if the experimental setup is similar to that ex- pected in the intended test, the value of X derived can be used to determine the percent of full scale zero shift that will occur under the

thermal condition of the actual test. Although the value of X derived

was determined by the average of five points taken during one previous

run, Table 2 is composed of data from six different runs picked because

they provided examples of differences in operating procedures that

covered the entire testing temperature range and measured zero shift.

Run number 1 was made on a unit which initially was slightly above room temperature and cooled by convection, i.e., no provision being provided

for additional air cooling. Runs numbered 2, 3, and 5 were initially at room temperature and cooled by convection currents. Runs numbered 4 and

6 were initially at room temperature and were cooled by forced air. A

fan directed room air on the exposed back of the transducer during the

test.

The relationship % FS zero shift = A • (manufacturer's coefficient

per degree) + X(A - B) is based on the limited data taken from the thermal

gradient measurements of thirteen different transducers. It is limited

in use to the zero shift after oil canning for various conditions of

front surface temperatures and resultant temperature gradients. It was found to be correct to ±10% for the flush diaphragm pressure transducers

tested.

The following example illustrates the procedure to be followed in

using the correction for a transducer under test. In this instance,

temperatures in °F are used to conform to the customary practice of
manufacturers in publishing transducer specifications. The empirical

relationship found for the gage of Figure 2c was 0.02% FS/°F (manufacturer's specification) plus 0.30% FS/°F (thermal transient test,

correction coefficient derived). One would therefore multiply 0.02 by

the temperature A of the front surface and then add the differential

term 0.30 (A - B) where B is the temperature of the back surface of the

transducer. One would then convert from % FS to psi and subtract this

value from the recorded pressure. The result would be the pressure

+10%, that would have been recorded if no thermal gradient had existed.

In this way correction is made for the zero shift of the transducer after

the first few seconds, provided the front and back temperatures of the

transducer have been monitored. An additional correction may be necessary

due to a change in sensitivity with temperature, although the error from

this source was not important in the devices that have been tested.

6. Effective Gradient Sensitivity

In order to allow comparisons among transducers tests at different

temperatures and with resultant different gradients, a relative "effective gradient sensitivity," (EGS) was calculated. The effective gradient

sensitivity was defined by dividing the maximum zero shift, in percent

of full scale, by the temperature difference between the hotter surface

of the transducer and the reference temperature for zero shift of the

transducer. The results are listed in Table 3 in terms of % FS/°F and

% FS/°C.

Since all the transducers were given the same kind of test, in each

case to the limit of the expected normal operating temperature, these

values (EGS) represent a measure of ability to perform while exposed to

thermal gradients. A transducer that has an EGS value that is equal to or less than the manufacturer's specifications for zero shift with

temperature can be considered to be unaffected by thermal gradients.

7. General Comments

As indicated in the earlier study 3 and verified by the tests re- ported here, design differences can be more important than the kind of

active element used in the transducer. Although both of the manufacturers

of the two pressure transducers used to obtain the test results shown in

Figures 4 and 5 used unbonded strain gages as their active elements, the

zero-shift response to thermal gradients differed widely.

The photographs in Figures 5a and 5b show the results of thermal

gradient tests on two transducers produced by the same manufacturer

eleven years apart. During this time, 1954 to 1965, the specification

3 loc cite,
for the upper operating temperature limit changes from 165°F to 250°F

and the zero shift specification was reduced from 0.08 to 0.015% FS/°F.

Some of the factors that govern the effect of a temperature gradient

are: the mass of the section exposed to the heat, i.e., the thermal

inertia of the case, the thermal path differences that exist between the

active elements and the compensating elements, the thermal alterations

of strain members, and changes in spring positions due to temperature

gradients in the supports. In addition, one could expect zero shifts to

result from "oil canning," leverage shifts due to unequal expansion of

parts, and variations in electrical and physical properties with temperature. These factors need to be considered in attempting to reduce or avoid the effect of thermal gradients.

To avoid the zero shift that is due to deformation requires a design

that allows for the thermal differences that are expected or are possible.

Balanced and compensated mechanical motions and thermal buffers for sensitive springs and flexures are possibilities. Fused Quartz or sapphire

rods for extensions to provide relatively constant dimensions and still

provide poor conduction of the heat would seem to be one way of removing

the active elements of the transducer from the immediate vicinity of the

heat source, thus producing a relatively constant environment that tends

to isolate and protect the active elements for short period of time.

One can transmit the pressure to be measured by tubes to a cooler

region (with altered dynamic characteristics) , or cool the active elements of the transducer by external means.

A compromise that would provide the equivalent of a uniform temperature zone for the transducer would consist of uniformly preheating the

transducer to within a few degrees of the expected working temperature

just before the test.

8 . Summary

Studies of the effects of thermal gradients on performance of pressure trandducers indicate that: 1. Flush diaphragm pressure transducers

may show very large zero shifts due to thermal gradients even though they

are compensated for changes in uniform temperatures. 2. For the thirteen

units tested, the detailed design is as important as the principle used

to convert diaphragm deflection to an electrical output signal, i.e.,

piezoelectric crystal, wire strain gages, bonded or not, differential

transformer, etc. 3. Some transducers can operate in a thermal gradient

with very little zero shift, but no simple way to predict this without

testing is apparent at this time.

Since the transducer's zero shift in this test is the result of an imposed thermal gradient and is a function of the transducer design, a comparison of responses to thermal gradients reflects the comparison of

transducer design features.
For the transducers tested, although the rate of energy input and

thermal flux density influenced the magnitude and the time to reach a given gradients, it is the temperature gradient itself that is responsible

for the zero shift of the instrument and this should be considered when

choosing a pressure transducer for field use.

The wide range of response that was encountered in these tests

emphasized the need for caution in interpreting the data furnished by

pressure transducers when thermal gradients may be present. While these

tests specifically aimed at conditions of temperature gradients in one particular direction, for gradients in other directions one can expect

comparable effects and they should be investigated by the user.
Transducer Type

(A) Unbonded wire strain

gages (damped and un- damped)

Unbonded wire strain

gages (damped and un- damped)

Unbonded wire strain

gages (damped and un- damped)

Unbonded wire strain

gages (damped and un- damped)

TABLE 1

Oil Canning

Pressure

Range

0-300

0-1000

0-50

0-15

% FS

1.0

- 3.0

1.0

30.0

Time to Reach

Maximum

(Seconds)

8.0

8.0

1.0

2.0

(B) Bonded strain gages

damped

0-500 8.0 1.0

(C) Semiconductor strain 0-100

gages

Semiconductor strain 0-100

gages

+ 2.0

+ 1.8

1.0

1.0

(D) Unbonded strain gage

Unbonded strain gage

(E) Variable inductance

Variable inductance

(F) Linear differential

transformer

0-150 -23.0 1.0

0-50 -10.0 0.1

0-100 - 2.5 1.5

0-100 - 5.0 1.5

0-500 none noted

(G) Crystal 0-3000 - 1.8 0.1
TABLE 2

Thermal Gradient Response

Temperature Temperature

Front Differential

Measured Measured

(A) (A-B)

228°F 47

180°F 63

300°F 60

253°F 120

545°F 120

360°F 160

Zero Shift

% FS

Computed Measured

0.02(A) + 0.3(A-B)

19 IS

23 25

24 25

41 44

47 49

55 50

10
TABLE 3

Effective Thermal Gradient

Figure Transducer Type Pressure Manufacturer's

Number Range EGS Specifications

% FS/°F % FS/°C % FS/°F % FS/°C

4a Unbonded wire 0-300 0.004 0.007 0.01 0.018

4b Unbonded wire 0-1000 0.01 0.02 0.01 0.018

Range

PSI

Unbonded wire 0-300

strain gages

(damped and

undamped)

Unbonded wire 0-100

strain gages

(damped and

undamped)

Semiconductor 0-100

strain gages

Variable

Inductance

0-100

0.01 0.02 0.01 0.018

0.018 0.03 0.01 0.018

0.03 0.05 0.01 0.018

0.043 0.08 0.01 0.018

0.073 0.13 none

3 Crystal 0-3000

3b $ c Bonded strain 0-500

gages damped

6 Linear 0-500

Differential

Transformers

2 Unbonded 0-150 0.083 0.15 0.02 0.036

strain

gages

5b Unbonded wire 0-50 0.10 0.18 0.015 0.018

strain gages

(damped and

undamped)

5a Unbonded wire 0-50 0.14 0.15 0.04 0.072

strain gages

(damped and

undamped)

11
Number

2b'

4c<

TABLE 3 (Continued)

Figure Transducer Type Pressure

Unbonded wire

strain gages

(damped and

undamped)

Unbonded wire

strain gages

(damped and

undamped)

Range

PSI

0-15

0-50

EGS

FS/°F % FS/°C

Manufacturer '

Specifications

i FS/°F % FS/°C

0.16 0.19 0.01 0.018

0.50 0.9 0.01 0.018

Figure 5a Received 1954

Figure 5b Received 1965

*The last two transducers require special mention. The 0-15 PSI gage

did return to manufacturer's specifications during the test within 50

seconds after the introduction of heat. The 0-50 PSI appears to have

a loose connection which separated under the stresses developed by a thermal gradient. The transducer did not show any abnormal output for

any of the standard tests and checked out within the manufacturer's

specifications in the normal temperature tests, both before and after

the thermal gradient tests. (See photographs 2b and 4c.)

12
TABLE 4

Response To Thermal Gradients

Transducer Pressure Test Maximum Time at

Type Range Temperature Zero Which

PS I °F Shift Maximum

% FS Occurs in

Seconds

Remarks

B

D

0-15 200 - 32 1-3

0-50 230 > + 100 30

0-300 212 + 1.0 50

0-1000 400 +4.0 180**

0-500 600 - 26 20

0-500 600 - 26 20

0-100 190 -2.0 31

0-100 190 -2.0 81*

0-150 600 + 49 51

0-50 160 + 22 10

0-50 250 + 26 8

Recovers to less than

3% FS by 51 seconds

After peak goes off

scale requires 10

minutes to recover

After peak at 50 seconds recovery starts

Maximum shift in- creases with time

After peak

After peak at 20 sec- onds recovery starts

After peak at 31 sec- onds recovery starts

After peak at 51 sec- onds recovery starts

After peak at 10 sec- onds recovery starts

After peak at 8 sec- onds recovery starts

0-100 250 +6.0 180 ** Maximum shift in- creases with time

0-500 320 23 180 ** Maximum shift in- creases with time

0-3000 373 - 10 After a peak at 7 sec- onds starts to recover

(test was limited to

20 seconds)

*Test Limited to 81 Seconds.

**Test Limited to 180 Seconds

13
14
1axc

•Hdauo « .

15
3.6 PSI (25 kN/or)

(a)

(b)

HI

««-* 7 pSI (32 kN/m2

) HI

Hfl 18 Ml 1 seconds

Unbonded Strain Gage

0-50 PSI

Time 2 S/cm

Temp. 165°F 74°C

Max Zero Shift + 23% FS

Unbonded Strain Gage

0-15 PSI

Time 18 S/cm

Temp. 200°F 93°C

Max Zero Shift - 32.7% FS

Unbonded Strain Gage

0-150 PSI

Time 17 S/cm

Temp. 200°F 93°C

Max Zero Shift + 25% FS

Figure 2 Thermal Gradient Response

16
(a)

Crystal

Range 0-3000 PSI

Time 2 S/cm

Test Temp. 373°F 189°C

Max Zero Shift - 10% FS

Bonded Strain Gage

Range 0-500 PSI

Time 17 S/cm

Test Temp. 600°F 316°C

Max Zero Shift - 26% FS

(b)

Bonded Strain Gage

Range 0-500 PSI

Time 17 S/cm

Test Temp. 600°F 316°C

Max Zero Shift - 25.6% FS

Figure 3 Thermal Gradient Response

17
(a)

- ! V

4.1+

1

i

!

t |30PSI (207 kN/m2

) ]

t

i : ' till:

i J_ fSH

H ^^"l

1 /

/"^ ± _- -*_

\\ / — HPH V 1 I

17

econds

J

- 1 (b)

\ III

10 PSI (69 kN/m2

) |

t

:|!l Hi'

, r

t Mil MM WF1 1 1.1 i 1 1 1 1 I II 1 M 1 i i

' IT? 1 1 i II

1

I'll MM

1

j

1 ! IH 1,1 I 1 1

f <

1 ! ! 1 ! I I

'

!

;

t 1

1 J

,—I*- ~*—

I V *%

. J^-r^

±

12

1 seconds I

1 (c)

Unbonded Strain Gage

Range 0-300 PSI

Time 17 S/cm

Test Temp. 212°F 100°C

Max Zero Shift 1.3% FS

Unbonded Strain Gage

Range 0-1000 PSI

Time 17 S/cm

Test Temp. 400°F 204°C

Max Zero Shift 4% FS

Unbonded Strain Gage

Range 0-50 PSI

Time 12 S/cm

Test Temp. 230°F 110°C

Max Zero Shift + 100% FS

Figure 4 Thermal Gradient Response

18
Unbonded Strain Gages

Range 0-50 PSI

Time 17 S/cm

Test Temp. 100°F 74°C

Max Zero Shift 23% FS

iBIHinn

6 PSI (41.4 kN/aT)

17

seconds

(b)

Unbonded Strain Gages

Range 0-50 PSI

Time 17 S/cm

Test Temp. 231°F 111°C

Max Zero Shift 30% FS

Figure 5 Thermal Gradient Response

19
Differential Transformer

Range 0-500 PSI

Time 17 S/cm

Temp. 320°F 160°C

Max Zero Shift + 23.4% FS

Variable Inductance

Range 0-100 PSI

Time 17 S/cm

Temp. 250°F 121°C

Max Zero Shift + 4.5% FS

(b) 1st 2.8 minutes

Conditions same as (b)

after 12th minute

Figure 6 Thermal Gradient Response

20
r[

' n | .8 PSI (5.5 Wra2

)

_—

k. t

Lj I Mil III \~~*~

1 1 1 I

i

I f s

I'M! It 1 !j_! ! 1 1

1

r-f-TT" Mr*?***4***«4

L i ! i \ EF^I

!

(a)

seconds ""

Semiconductor Gages

Range 0-100 PSI

Time 9 S/cm

Temp. 193°F 89°C

Max Zero Shift 1.9% FS

.8 PSI (5.5 kN/m2 )|

Wm\ h

tm>^m**

seconds 1

(b)

Semiconductor Gages

Range 0-100 PSI

Time 17 S/cm

Temp. 193°F

Max Zero Shift 1.9% FS

Figure 7 Thermal Gradient Response

21

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