Within many factories and industrial plants, Temperature Transmitters are becoming increasingly popular instruments.
Just as with any other measuring instruments, it is important that they are regularly calibrated so that they can perform their functions and provide accurate readings. In this article, we will discuss how that calibration process can be achieved.
But before we get there, let us just discuss –
What is a Temperature Transmitter?
To ensure that this article will discuss the calibration of the types of instruments you are dealing with, let us briefly clarify what a temperature transmitter is.
Temperature Transmitters work to assist in the monitoring of temperature in a remote process. They convert temperature readings to a signal that can be transmitted to a range of instruments that convert the signal to data that can be read and recorded.
Because of the nature of both of their operation and the fact that they essentially transmit data, it is important they are correctly calibrated so they are as accurate as possible.
How to Calibrate a Temperature Transmitter
So now we know what we are talking about, and why it’s important to calibrate it, the next stage is to discuss the calibration process itself!
We should note at this stage that there is not a universal method that will cover the calibration of all Temperature Transmitter devices. There are quite simply too many devices from different manufactures on the market to make that claim.
Instead, we will discuss a more general-purpose guide that covers the basics of the calibration process for this instrument. If in doubt, it is highly recommended that you refer to the original instructions of your transmitter, that you contact the original manufacturer for advice and guidance or that your consult a professional calibration company.
So just as with any other process, the first thing to do of course is to gather all of the equipment and materials that will be required for the job.
As we discussed above, this equipment list could alter slightly depending on the specifics of your own transmitter. As a general rule of thumb however, you will require:
- A digital Voltmeter rated to 1mv. This is the key piece of equipment in the calibration process so it should be a model with as high a degree of accuracy as you can find.
- A power source, of a voltage of the same level used to power the transmitter.
- A Resistance Decade Box. Again, this should be a model with the highest precision you can find.
- You will need to remove the housing cover on the transmitters, so you will also need suitable tools for his, i.e. screwdrivers or wrenches.
- The first step is to disconnect power, and then to remove the housing cover from the transmitter so that you can gain access to the transmitter terminal itself.
- If the transmitter has recently been operational, the RTD (Resistance Temperature Detector) may still be connected. If this is the case, disconnect it now, including all lead connections.
- Make sure that the RTD resistance is set to the required level (i.e. 0 Celsius)
- Turn the power supply on.
- On the Resistance Decade Box, set a resistance that corresponds to the required base temperature, adjusting the potentiometer on the transmitter itself until output is reading a steady 4mA.
- Repeat step 5 except this time you are setting the decade box to the resistance that corresponds with the full temperature instead of the base. Again, adjust the potentiometer on the transmitter until it reads 20mA in this instance.
- Repeat steps 5 & 6 until readings of 4 and 20mA are achieved at each respective temperature with no adjustment.
- Remove all tools, replace transmitter cover and secure into position.
Congratulations, you have calibrated your Temperature Transmitter!