Watlow ez-zone pm - Output Configuration and Control Methods

Watlow EZ-ZONE
®
PMI Controller • 186 • Chapter 9 Features
Calibration
Before performing any calibration procedure, verify that the displayed readings are not
within published specications by inputting a known value from a precision source to the
analog input. Next, subtract the
displayed value with the known
value and compare this differ-
ence to the published accuracy
range specication 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 read-
ings across the entire displayed
range by the offset value. Use
this parameter to compensate
for sensor error or sensor place-
ment error. Typically this value is
set to zero.
Equipment required while performing calibration:
Obtain a precision source for millivolts, volts, milliamperes or resistance depending on the
sensor type to be calibrated. Use copper wire only to connect the precision source to the
controller’s input. Keep leads between the precision source and controller as short as possi-
ble 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
Time
Temperature
Temperature Reading
from Sensor
Actual Process Temperature
Negative Calibration Offset will
compensate for the difference
between the Sensor Reading and
the Actual Temperature