10-3
10.2 RTD / POT Calibration
All HiD range of isolator are designed for long term stable and trouble free operation. They have been factory
calibrated using high accuracy, periodically certified, traceable standard calibrators operating under computer
control to perform an automated Final Testing procedure and Test Data Recording. Therefore they should not
require, under normal operating circumstances, any calibration check or readjustment.
For input type or range modification, however is necessary re-calibrating the output scale to adjust to the new input
values.
10.2.1 Equipment required
In case a calibration check or readjustment is necessary the following equipment is required:
• 4 ½ digit digital multimeter
Range 20 V, resolution 1 mV, accuracy ±0.1% or better
Range 20 mA resolution 10 µA, accuracy ±0.1% or better
• RTD: precision decade resistance box
Range 0-400 Ω, resolution 0.01 Ω, accuracy ±0.03% or better
• POT: two precision decade resistance box
Range and resolution depending on POT value, accuracy ±0.03% or better
10.2.2 RTD or POT Input range modification
In case of input type changing you must configure the instrument according to the procedure given in section 5.10
In case of input range changing, the input range setting dip-switches position must be changed following the
procedure:
1) Find the required input type at the paragraphs 10.1.1 to 10.1.2 ( example Pt 100 Ω at 10.1.1).
2) Select the Zero and Span tables that better satisfy the range extension required (i.e. –200 to +500 °C).
3) Find on the Zero table the value closest to the one to be calibrated (i.e. 0 for a range 0 to +300 °C) and set the
switches SW3 accordingly.
4) Find on the Span table the value closest to the one to be calibrated (i.e. +290 °C for a range 0 to +300 °C) and
set the switches SW3 accordingly.
5) Proceed then in calibrating the front accessible trimmers for fine adjustment output value based on input
signal range.
6) If the calibration is difficult, select on the Zero and Span tables a new range close to the previous one and
repeat the calibration procedure.
10.2.3 Pt 100 ΩΩ RTD Input range calibration
Connect the decade resistance box at the input terminals of the unit and the multimeter at the output terminals
(current or voltage mode dependent to the output type). Allow five minutes for warm up the unit, then set the
decade box at low end of scale signal and check the output value. It should also be at low end of scale. Adjust if
necessary, the ZERO trimmer of the relevant channel.
Set the decade box for full scale value, check the output value that must also be at full scale and adjust, if
necessary, the SPAN trimmer of the relevant channel.
Return to the low end of scale and check for shifting of calibrated value. If necessary re-adjust the output value
until it comply with the specified accuracy.
If a burnout feature is specified, open any of the 3 input wires (or any combination) and check that the output goes
beyond full scale for UP SCALE burnout or below low end of scale for DOWN SCALE burnout.
10.2.4 Other types of RTD (to be specified when ordering)
On specific request, different type of RTD sensor can be configured, for linear temperature output in the converter
(i.e. Pt 100 ANSI or Ni 100 or Cu 10).
Differences from Pt 100 DIN mainly stems from some component value on the base board bridge circuit and/or
some values on the input preamplifier circuit.
The calibration procedure is very similar to that described above.
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