Configure RTD channels for temperature measurements

Using PiCtory, you can configure your RevPi AIO module. In this chapter, we will describe the Value Editors settings for the RTD channels in greater detail. If you are not familiar with RTD measurements, have a look at our our tutorial “basic knowledge RTD measurements“.

Requirements:

  • You have a web browser installed on your computer (e.g. Chrome or Firefox).
  • RevPi Core is located in your network.

Let’s go!

Your RevPi AIO has two 2 RTD channels. It means you can measure temperature using connected Pt100 and Pt1000 sensors.

In order for your configuration to function, it’s important that your devices are connected up to the right input pins.

RevPi AIO RTD channel pinout
RTD graphic

Please remember that the AIO module is used for a 2-wire sensor that uses the three-wire measurement system. Therefore, you basically have to simulate the missing third wire with a jumper between pins 10 and 12 and 9 and 18 respectively.

  • Open your web browser.
  • Enter the IP address of your RevPi Core in the address bar of your web browser.

The login window appears.

pictory-anmelden
  • Log in with the username “admin”.
  • Enter the password. You can find it on the sticker on the side of your RevPi Core.
  • Click on “Login”.

You will now see the current device status of your RevPi Core.

Apps tab Screenshot
  • Click the “Apps” tab.
  • Click the start button behind the entry “PiCtory”.

PiCtory opens.

  • Open the folder “I/O Devices” in the device catalogue
  • Select the AIO module
  • Drag and drop the AIO in the empty slot on the configuration board.
  • Set the basic settings for your adapters in the “Device Data” window. This entry is optional. If you use a lot of devices and want to process the data later in another program, this input can be very useful.

You can configure the RTD channels in Value Editor. The detailed setting can be found in the following table:

Description Value Comment
RTD1Type,
RTD2Type
  • Pt100
  • Pt1000
Set here which type of measuring sensor you are using.
RTD1Wiring,
RTD2Wiring
  • 2-Wire
  • 3-Wire
  • 4-Wire
Select here the measurement process that is suitable for your temperature sensor.
RTD 1 scaling
RTD1Multiplier
RTD1Divisor
RTD1Offset
RTD 2 scaling
RTD2Multiplier
RTD2Divisor
RTD2Offset
  • 16 Bit signed Multiplier
  • 16 Bit unsigned Divisor
  • 16 Bit signed Offset
Set here the scaling for the RTD channels. It is determined by means of the three configuration values and calculated in accordance with the following formula from the original value (which exists in 1/10 °C):

Y = Multiplier/Divisor*X + Offset

The scaling can subsequently be used for conversion in other units or for a subsequent calibration of a temperature sensor. A 32-bit integer arithmetic is used for calculations in the AIO module. The results are then however stored as 16-bit values in the process image. Should the result Y exceed the limits of a 16-bit signed value, then the fault will be recognised and the value limited.

Example:

To have the temperature shown in °C without positions after the decimal point in the process image, then the setting has to look like this:

Multiplier = 1, Divisor = 10, Offset = 0

To have the temperature to be shown in °F in the process image, the parameter have to be set as such:

Multiplier = 18, Divisor = 100, Offset = 32

For process data in °Kelvin, you need these values:

Multiplier = 1, Divisor = 10, Offset = 273

  • Click on „File>Save“ to save your file.
  • Click on “Tools>Reset Driver”. You thus activate the changes for the adapter.

Should an error occur, then you will receive error message in the input values of the process image with names, Bytes RTDStatus_1 and RTDStatus_2. The values have the following meanings:

Bit position Meaning Comment
Bit 0 (LSB) 0 = temperature is higher than -200 °C,

1 = the recorded temperature is lower than -200 °C (e.g. short circuit in sensor or cable)

Should the recorded temperature be outside the range, the respective limit will be issued (-200.0°C or 850.0°C) and the respective status bit will additionally be set.
Bit 1 0 = temperature is lower than 850 °C,

1 = the recorded temperature is higher than 850°C (e.g. a sensor isn’t connected or cable breakage).

You can establish symbolic names for the two temperature values in the RTDValue_1 und RTDValue_2 fields. Under these names you can then, using PiTest, a programme you’ve written yourself or an application software, read measurement values of the connected sensors from the process image.

Would you like to continue to use the settings in logiCAD3, Python or C

  • Click on “File>Export”.

A window will now open. You can determine the file format and specify the file name.

You can choose between 2 formats:

Export 01 creates a file suitable for use in logiCAD3.
Export 02 creates an offset list that you can use as basic information for your own C or Python programme.

  • Select a format with which you would like to continue to work.
  • Enter a file name
  • Click on „Ok“.