Emerson 381 instruction manual Temperature vs Resistance of Auto, Element

Page 22

MODEL 381pH/ORP

3.4PREAMPLIFIER TROUBLESHOOTING. To deter- mine if the preamplifier is operable, proceed as follows:

1.

Remove the sensor from process.

2.

Remove the cover from the body by grasping the

SECTION 3.0

MAINTENANCE

TABLE 3-2

TEMPERATURE vs RESISTANCE OF AUTO

T.C. ELEMENT

 

body and rotating the cover 1/4 turn in the count-

 

er-clockwise direction.

3.

When the cover breaks loose from the body, pull

 

straight out on the cover to expose the com-

 

ponents attached to the body and disconnect the

 

BNC connector from the preamplifier, leaving the

 

cable connected. Inspect the internal preamplifier

 

area for signs of moisture or corrosion; moisture

 

can short out the preamplifier. Dry all parts thor-

 

oughly before testing.

4.

Short the center pin of the BNC on the preamp-lifi-

 

er to the outside of the BNC connector.

5.

The meter indication should be approximately

 

center scale (7 pH).

6.

If the meter indication is not as specified in Step 5,

 

proceed to the transmitter instruction manual for

 

further troubleshooting. If the transmitter is opera-

Temperature °C

0

10

20

25

30

40

50

60

70

80

90

100

Resistance

(Ohms) ± 1%

3K PT-100

2670 100.0

2802 103.8

2934 107.7

3000 109.6

3066 111.5

3198 115.4

3330 119.2

3462 123.1

3594 126.9

3726 130.8

3858 134.6

3990 138.5

 

ble with the preamplifier bypassed, then the pre-

 

amplifier is defective.

7.

Unplug the preamplifier from the body.

8.

Plug a new preamplifier into the body.

9.

Plug the BNC connector of the glass electrode into

 

the preamplifier.

10.

Make sure all O-rings are clean, lubricated and in place.

11.

Plug the cable connector into the preamplifier, making

 

sure the cable is towards the center of the body.

12.

Install the cover on the body so that the threads

 

engage.

13.

Rotate the cover until the triangle on the body

 

aligns with (or falls within) the adjacent mark on

 

the cover.

CAUTION

DO NOT use a pipe wrench on the body or cover. Severe damage could result.

14. Install the sensor as described in Section 2.0.

3.5T Automatic Temperature Compensator. The temper- ature compensator element is temperature sensitive and can be checked with an ohmmeter. Resistance increases with temperature.

The 3K element will read 3000 ohms ± 1% at 25°C (77°F) and a Pt-100 will read 110 ohms. Resistance varies with tem- perature for a 3K and Pt-100 element and can be determined according to Table 3-2 or the following formula:

RT=Ro [l+R1 (T-20)]

Where RT = Resistance

T = Temperature in °C

Refer to Table 3-3 for Ro and R1 values

TABLE 3-3

Ro and R1 VALUES FOR TEMPERATURE

COMPENSATION ELEMENTS

Temperature

Ro

R1

Compensation Element

 

 

 

 

 

3K

2934

.0045

PT-100

107.7

.00385

 

 

 

18

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Contents PH/ORP Sensor Essential Instructions Model 381 pH/ORP Sensor About This Document Section Description and Specifications Features and ApplicationsMeasuring Range pH Sensor SpecificationsMaterials of Construction Pressure Rating 790 kPa abs at 100C 100 psig at 212FExample Page Section Installation Model 381 Sensor Component Locator Diagram Section Submersion Installation Diagram Flow Through Installation Diagram Code 03 or Retro-Fit Kit Code 04 Flow Powered Cleaner, Model 40038105 40038103 40038116 Model 381 ORP START-UP and CalibrationCalibration Section Maintenance Temperature C Millivolt Potential 268 264 260 Troubleshooting Probable Cause Remedy Temperature Temperature vs Resistance of AutoElement Accessories Model 381 Spare PartsPage Section Ultrasonic Cleaner Operation 40038156 40037505 NON Warranty Repair Section Return of MaterialReturn of Materials Request Warranty Return of MaterialSpecifications subject to change without notice