Hi Jaya,
I think the problem is either the heater is shorted and the VTU is drawing
too much current or the VTU for some reason isn't able to provide current
to the heater. So the unit applies a voltage and the current limiter kicks
in because it is measuring too high a current and cuts the voltage back
down to zero. In the manual it may specify what the heater
resistance should be. Anyway I would measure this first.
Cheers,
Chuck
On Thu, Apr 2, 2026 at 2:06 PM Jaya Nolt via groups.io wrote:
> Hi Ammrl group,
> I am looking for some troubleshooting help with our probe heater. Our EPR
> is running Xenon with the VTU device.
> Software says probe heater is OK however no heater power comes on, and it
> stays at 0%. In the webpage I can turn on the heater briefly by clicking on
> the options for 10%, 30% etc. I can see the heating effect and then the
> percent drops back to 0.
> One guess is that the heater safety sensor is not working properly.
> The other guess is that the PID values have been comprimised.
> In the software VTU controls there are no PID values listed in the table,
> it is grayed out, and loading PID values is not supported. This seems odd
> but I don't have any documentation otherwise. Also I cannot find anything
> in the calibration files for VTU values.
>
> Thanks for any thoughts in advance.
>
> Jaya
>
--
Charles Hanson
Assistant Director, Magnetic Resonance Center
Boston College
Merkert 107
2609 Beacon Street
Chestnut Hill MA 02467-3860
Tel (617) 552-6903 (office)
https://www.bc.edu/content/bc-web/research/sites/vice-provost-for-research/about/research-facilities/nmr-center.html
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Received on Thu Apr 02 2026 - 11:23:11 MST