Notes for installation and commissioning

The accuracy of the TC-temperature-measurement is directly affected by the cold-junction-measurement. So some design guidelines have to be followed!

  • Use high quality PT1000 with low tolerance, put the PT1000 very close to the TC-connector on the backplane or wherever the cold-junction is located.
  • Avoid parasitic resistances in the RTD-circuit e.g. bad connection or long leads,+3 Ohms → +1°C.
  • Put ground-shield around the traces to avoid emi-disturbances.
  • Avoid excessive external heating (e.g. near transformer) or cooling (e.g. air flow) of the PT1000 sensor so that its temperature becomes significantly different from the connector of the TC-elements.
  • Wire-calibration can be done with indexes 0x8080:1B and 0x8090:1B.

Notes for measurement of cold-junction-temperature

Measurement and calculation of the correct temperature with TC-elements require also to measure the so called cold-junction-temperature. The cold-junction-temperature is measured by two RTDs. They should be connected very close to the connection of TCs onto the backplane (change from TC-material to copper).

Notes for installation and commissioning 1:
TC/ RTD connectors on the backplane

Examples:

  1. One isothermal block → all TC-connections on the backplane are located closely at one place and have the same temperature:
    • one RTD is sufficient, any TC can be referenced to e.g. “RTD1”
  2. Notes for installation and commissioning 2:
    One isothermal block
  3. Two isothermal blocks with different temperatures and each with an own RTD:
    • the number of TCs on the one and the other block can be freely selected, e.g. TCs 1-3-4-7-8 close to RTD1 and TCs 2-5-6 close to RTD2.
  4. If there is a temperature gradient along the connecting terminals of the TCs,
    • an average temperature of RTD1 and RTD2 could be calculated by a PLC and provided as process data.
    • In this case the TC-channels 1 .. 4 should be referenced to CJ1, the TC-channels 5 .. 8 should be referenced to CJ2.
  5. Notes for installation and commissioning 3:
    Temperature gradient along the connecting terminals of the TCs
  6. If necessary the TC-channels can be routed to two different TC-connectors. Follow the rules mentioned above!
Notes for installation and commissioning 4:
TC-channels routed to two different TC-connectors

Settings of coldjuction compensation

Preset for each channel is intern RTD Ch1, the assignment can be chosen separately for each channel in index 0x80n0:0C (n=0: Channel 1 .. n=7: Channel 8).

Notes for installation and commissioning 5:
TC Settings taking Ch.1 as an examplen, Index 0x8000:0C
Notes for installation and commissioning 6:
CJC selection dialog

Name

Value

Description

intern RTD Ch1

0dec

The coldjunction compensation takes place via intern RTD Ch1 of the module (default).

no

1dec

The coldjunction compensation is not active

extern processdata (1/10°C)

2dec

The coldjunction compensation takes place via the process data 0x160n (n=0: Channel 1 .. n=7: Channel 8). These must then be mapped via the PDO assignment.

intern RTD Ch2

3dec

The coldjunction compensation takes place via intern RTD Ch2 of the module.

Other settings:

  1. Filter: the index 0x8000:15 is valid for all channels, default 50 Hz
  2. Index 0x80x0:18 - TC element setting for each channel separately