USB-TC temperature variations

[Jane]

Hi,

I used a USB-TC connected to a T-type thermocouple wire to measure temperature. However, the measured temperature from the USB-TC and thermocouple is around 4 to 5 degrees Celsius lower than that of the mercury thermometer. Are there methods (like calibration) we can use to correct the variations? I attached the USB-TC device for your reference.

Looking forward to hearing from you.

Thanks,

Jane

 

Edited January 26 by Fausto
Removed invoice with contact information.

[Fausto]

Hello @Jane.

How many thermocouples are connected to this module and are they shielded thermocouples?

The thermocouple connections should begin with input channel CH0.

Which software application are you using with the MCC USB-TC?

In software, select only those channels with a connected thermocouple.

Did the thermocouple vendor provide you with accuracy specifications for the thermocouples?

As mentioned in the user's guide, "allow the USB-TC to warm up for 30 minutes before taking measurements. This warm up time minimizes thermal drift and achieves the specified rated accuracy of measurements."

The thermocouple tips should not be in direct contact with a metal surface.  Recommend using a thin film tape or an epoxy at the end of each thermocouple.

How long are the thermocouples?

If there are any pumps, motors or ovens near the thermocouples, you will need to add some type of shielding.

Regards,

Fausto

[Jane]

Hi Fausto,

Thank you for the quick response. Please see the following clarifications in my case. 

How many thermocouples are connected to this module and are they shielded thermocouples?

One 

The thermocouple connections should begin with input channel CH0.

Yes, the thermocouple wire was connected with CH0. 

Which software application are you using with the MCC USB-TC?

We used the software TracerDAQ. 

In software, select only those channels with a connected thermocouple.

Yes, it is the way we do.

Did the thermocouple vendor provide you with accuracy specifications for the thermocouples?

No. The thermocouple wire we used is OEMGA Fine Gage Thermocouple Duplex Wire TT-T-30-SLE-25 (https://www.omega.com/en-us/temperature-measurement/temperature-wire-and-cable/thermocouple-wires/finewire-dupinsul/p/TT-T-30-SLE-25)

As mentioned in the user's guide, "allow the USB-TC to warm up for 30 minutes before taking measurements. This warm up time minimizes thermal drift and achieves the specified rated accuracy of measurements."

Yes, the USB-TC was warmed up more than 30 min before we used it.

The thermocouple tips should not be in direct contact with a metal surface.  Recommend using a thin film tape or an epoxy at the end of each thermocouple.

No, the thermocouple tip was in a water bath without touching any metal surface.

How long are the thermocouples?

The thermocouple wire is about 1.2 meters in length. 

Does the USB-TC or Software TracerDAQ need any calibration before we use them? Is there any process we should follow to ensure the measurement accuracy?

Thanks,

Jane

[Fausto]

Hello @Jane.

Thank you for your responses. 

Please confirm that the analog input channels are configured for Type T thermocouples, in InstaCal.

 

From the top menu in InstaCal, click on Calibrate followed by A/D to calibrate the internal circuitry.  Afterwards, from the top menu, click on Test followed by Analog.  Select the channel with a connected thermocouple and then press the Test button.

 

Please test the other input channels individually with that thermocouple.  How do the channels compare with each other?

Did you create that thermocouple from the thermocouple wire by twisting the end?

Do you have another thermocouple, to test with the USB-TC, that was not cut from a wire spool and twisted; one with a soldered tip?

Do you have another calibrated temperature instrument to use as a reference?

What is the serial number of the USB-TC as shown on the backside label of the module or in InstaCal?

Is this a new USB-TC module or has it been used in the past without any issues?

 

Regards,

Fausto

[Jane]

Hi Fausto,

Thank you so much for the information and questions. 

I calibrated it following your instructions. After the calibration, the room temperature values were ~21C, determined by the thermocouples (please see details in attachment). In contrast, the mercury thermometer and another temperature sensor values were ~22C (details in attachment). There are slight differences among channels.

Did you create that thermocouple from the thermocouple wire by twisting the end?

Yes, we twisted the wire end.

Do you have another thermocouple, to test with the USB-TC, that was not cut from a wire spool and twisted; one with a soldered tip?

Unfortunately, we only have one type of thermocouple. We used two thermocouple wires. Both displayed similar values but ~1C lower than the mercury thermometer.

Do you have another calibrated temperature instrument to use as a reference?

We used mercury thermometers and a digital thermosensor as references. 

What is the serial number of the USB-TC as shown on the backside label of the module or in InstaCal?

The serial number is 20F3D59. 

Is this a new USB-TC module or has it been used in the past without any issues?

This is a new USB-TC module.

[Fausto]

Hello @Jane.

Thank you for the responses.

As a rule of thumb, please connect the thermocouples beginning with CH0.  What are the readings for thermocouples in channels CH0 and CH1?

Please send me a private message with the original sales order/invoice to start the process for a calibration RMA.  The device is sent back to the factory for recalibration.

The thermocouple measurement accuracy table of the USB-TC is shown on page 14 of the USB-TC user's guide.

Regards,

Fausto

[Jane]

Hi Fausto,

Thank you for the quick response. The readings in channel 0 and channel were 21.130 and 21.095, which were displayed in the pic that I sent to you in the last message. 

The invoice was in the attachment. About sending the device back to the factory for recalibration, how long may it take for the whole process? 

Thanks,

Jane

 

Edited July 29 by Fausto
removed contact info

[Fausto]

Thank you @Jane.

I will send you a private message regarding the calibration since the USB-TC is less than a year old.

Regards,

Fausto