Racegrade TC8 + Omega Thermocouples

[hamer]

I ordered a couple Omega 1/8 NPT Type-K Thermocouples (https://www.omega.com/en-us/temperature ... -8NPT-G-72).

I'd like to use them on the RG-TC8. They only have a range up to 650C unlike the standard Type-K that goes to 1250C. The instructions for the TC8 note that we should select the "E888 Expander Thermocouple" for the calibration file. Will this hold for the Omega 650C Thermocouples? I see the calibration is Ratiometric 5V with 5V = 1250C. Would the Omegas just use less voltage? Or should they be rescaled to 5V = 650C?

Thank you!

[Stephen Dean]

Hi,

I would recommend contacting MoTeC US support (support @ motec . com) with this question as they work with RaceGrade on this hardware.

[hamer]

For anyone else interested, this is the answer I got from MoTeC US Support:

The 650°C rating from Omega will be with respect to the installation not the sensing element. All K-Type thermocouples have the same calibration curve, but not all packaging can tolerate the maximum ratings the sensing element can resolve. As an example, if this same thermocouple were encased in plastic it would have a much lower maximum permissible range, but underneath it all it could still resolve to 1250°C. Please use the standard calibration as recommended and if you are concerned run a test with boiling water just removed from it's heat source. You should see 100°C +/- 2%

[David Ferguson]

Kids these days -- they think that water boils at 100degC -- uh, only at sea level. At 6000 ft, it's only 93.8 degC.

[hamer]

Kids these days -- they they think that water boils at 100degC -- uh, only at sea level. At 6000 ft, it's only 93.8 degC.

That's the truth.

I appreciate the help Dave, another issue popped up today. The readings on the RG-TC8 are reasonable, however as soon as I spin the rear wheel the temp readings start to fluctuate quite a bit like there's some type of electrical noise. I've tried grounding the shield of the thermocouple, and/or the negative end of the thermocouple with no luck. Any thoughts?

[Stephen Dean]

Hi,

Where are the wheel speeds being read? is there any common wiring between the wheel speed sensors (sensor type as well), the RG-TC8 and whichever device is reading both.

[hamer]

Hi,

Where are the wheel speeds being read? is there any common wiring between the wheel speed sensors (sensor type as well), the RG-TC8 and whichever device is reading both.

Hi Stephen,

We aren't running wheel speed sensors on the bike. The RG-TC8 is on CAN bus 2 on the C125, running the default address. It is the only device on that CAN bus. The 12V to the TC8 is shared with the C125. I've measured the 12V signal and it's rock solid. Just want to note this is an EV, so spinning the rear wheel means sending amps from the battery to the motor.

I've looked at the wiring and haven't seen anything glairing.

[David Ferguson]

I've seen problems with bad insulation on HV motor leads leading to voltage swings on the ground. Check your motor case. The symptom was loss of CAN communications. So you may find that your CAN data is returning to it's default value when the CAN data from the TC8 isn't received.

[David Ferguson]

I suggest putting an oscilloscope on the CAN lines to look for noise.

[Stephen Dean]

I'd also put a scope on one of the TC signal wires to see if the voltage is swinging, or as Dave said, it may be interference with the CAN Bus.