Watlow EZ-ZONE PM User Manual download pdf (Page 77)

Watlow EZ-ZONE

PM Limit Controller • 74 • Chapter 8 Features

Calibration

Before performing any calibration procedure, verify that the displayed readings are not within published

specifications by inputting a known value from a precision source to the analog input. Next, subtract the dis-

played value with the known value and compare this difference to the published accuracy range specification

for that type of input.

Use of the Calibration Offset [`i;CA] parameter found in the Operations Page [oPEr] , Analog Input

Menu [``Ai] shifts the readings across the entire displayed range by the offset value. Use this parameter to

compensate for sensor error or sensor placement error. Typically this value is set to zero.

Equipment required while performing calibration: Obtain a precision source for millivolts, volts, milli-

amperes or resistance depending on the sensor type to be calibrated. Use copper wire only to connect the pre-

cision source to the controller’s input. Keep leads between the precision source and controller as short as pos-

sible to minimize error. In addition, a precision volt/ohm meter capable of reading values to 4 decimal places

or better is recommended. Prior to calibration, connect this volt/ohm meter to the precision source to verify

accuracy.

Actual input values do NOT have to be exactly the recommended values, but it IS critical that the actual

value of the signal connected to the controller be accurately known to at least four digits.

Calibration of Analog Inputs:

To calibrate an analog input, you will need to provide a source of two electrical signals or resistance values

near the extremes of the range that the application is likely to utilize. See recommended values below:

Sensor Type Precision Source Low Precision Source High

thermocouple 0.000 mV 50.000 mV

millivolts 0.000 mV 50.000 mV

volts 0.000V 10.000V

milliamps 0.000 mA 20.000 mA

100ΩRTD 50.00Ω 350.0Ω

1,000ΩRTD 500.0Ω 3,500Ω

thermistor5kΩ 50.00 5,000

thermistor10kΩ 150.0 10,000

thermistor20kΩ 1,800 20,000

thermistor40kΩ 1,700 40,000

potentiometer 0.000 1,200

Note:

The user may only calibrate one sensor type. If the calibrator interferences with open thermocouple detec-

tion, set Sensor Type [`SEn] in Setup Page [`SEt], Analog Input Menu [``Ai] to millivolt [`Mu] instead

of Thermocouple [``tC] to avoid interference between the calibrator and open thermocouple detect circuit

for the duration of the calibration process. Be sure to set sensor type back to the thermocouple type utilized.

1. Disconnectthesensorfromthecontroller.

2. Record the Calibration Offset [`i;CA] parameter value in the Operations Page [oPEr] , Analog Input

Menu [``Ai] then set value to zero.

3. Wiretheprecisionsourcetotheappropriatecontrollerinputterminalstobecalibrated.Donothaveany

other wires connected to the input terminals. Please refer to the Install and Wiring section of this manu-

al for the appropriate connections.

4. Ensure the controller sensor type is programmed to the appropriate Sensor Type [`SEn] to be utilized in

the Setup Page [`SEt] , Analog Input Menu [``Ai] .

5. Enter Factory Page [FCty], Calibration Menu [`CAL] via RUI or EZ-ZONE Configurator Software.

6. Select the Calibration [CAL] input instance to be calibrated. This corresponds to the analog input to be

calibrated.

7. Set Electrical Input Slope [ELi;S]to1.000andElectricalInputOffset[ELi;o] to 0.000 (this will cancel

any prior user calibration values)

8. Input a Precision Source Low value. Read Electrical Measurement value [`Mu] of controller via

EZ-Configurator or RUI. This will be referred to as Electrical Measured Low. Record low value

______________

9. Input a Precision Source High value.

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