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Alternative for thermocouple measurements

Siemens Theorist Siemens Theorist
Siemens Theorist

Simcenter SCADAS hardware offers several ways to measure temperature sensors from eight chanimage.pngnels to several hundreds of channels. The standard solutions for Simcenter SCADAS Mobile or Lab are available through SCM/SCL-T8 card or through a CN4 card in combination with the TCK-8 module.

 

However, there are some cases, when only one or just a few sensor measurements are needed, that even eight input channels is just too much.

 

Luckily, there is an alternative solution through a “linear thermocouple amplifier” from Michigan Scientific Corporation. The product is called MicroTC and is intended for thermocouple conditioning and can be used in combination with a standard Simcenter SCADAS DB8/VB8 input module.

 

The MicroTC is a single channel non-isolated, pre-conditioned temperature input, for K-type thermocouples. The amplifier is powered from an DC-Supply – for example the supply from the input module – and has two versions, The MicroTC-S and MicroTC-D:

 

  • The –S is single supply version and uses a supply voltage between + 7Volts and +16 Volts.
  • The –D is Dual Supply version and needs 2 supply voltages e.g. from ± Volts to a maximum of ±16 Volts. The operating current max will be 3.25 mA.


Both versions have a sensitivity of 5mV per degree Celsius over a wide linear input range.

 

How to connect it to a analog input module?

image.png
As mentioned earlier, the MicroTC can be powered and measured with Simcenter SCADAS DB8/VB8 modules.


Making a connection requires a LEMO to pigtail cable and some soldering work, based on the following pinning layout:

 

Micro TC:

DB8/VB8

Wire color

V+

Pin 1 +VSupply

White

S+

Pin 3 +In

Grey

G

LEMO shell, pin 4 Ground -In

Black

Pink

V- * (-D Dual supply only)

Pin 6 -VSupply

Brown

 

 

Once the wiring is done, here’s how to make a proper channel setup in Simcenter Testlab:

 

Micro TC

Version

Testlab Channel Setup

Power Supply Voltage

Linear range

Celsius

Polynomial range

Celsius

Micro TC: - D

Sensor with Excitation Differential

10 Volts  (-5 V  to + 5 V)

-50 to +400

-200 to +800

Micro TC: - S

Active Sensor Differential

14 Volts

+5 to +400

+5  to +1360

 

The dual supply MicroTC-D is configured in the channel setup of Simcenter Testlab as “Sensor with  Excitation differential”. With this setup, the maximum DC supply voltage available from DB8/VB8 will be +5Volts and -5Volts.

 

The single supply MicroTC-S is configured in the channel setup of Simcenter Testlab as “Active Sensor Differential”. In this case, the supply voltage for VB8-III will be +14 Volts.

 

If the channel setup is complete, the last step before acquiring is to configure linearization formulas. The output of the MicroTC is linear 5mV/°C over an input range of -50 to 400 °C (5 to 400 °C for single-supply). Outside of that range, linearizing formulas needs to be used. This helps determine if the temperature remains within the specified error levels.

 

The following formulas will convert the voltage values from the amplifier as the independent variable and generate temperature in °C.

 

Micro TC: -D: Dual Supply

Range: -60 to 800 °C

T = -0.00036 x V6 – 0.0031 x V5 + 0.1248 x V4 – 0.014 x V3 – 4.419 x V2 + 207.488 x V – 1.1

 

NOTE: The +5 Volt supply limits the upper temperature part to a maximum of 800 °C.

Range: -200 to 100 °C

T = -142.644 x V4 + 30.529 x V3 + 3.504 x V2 + 207.53 x V – 0.1077

 

Micro TC: -S: Single Supply

Range: 5 to 1360 °C

T = 0.02327 x V4 + 0.5818 x V3 – 5.5369 x V2 + 208.0778 x V – 1.9183

T = Temperature in °C

V = Voltage from amplifier

 

Formulas can be entered in Time Signal Calculator or Virtual Channels. 

 

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