Watlow EZ-ZONE PM - Manual (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.