4 replies to this topic

[pep.]

Since last week, I'm a proud owner of a Polyscience Sous Vide Professional. Following Pedro's recommendations in Sous Vide Wiki, I checked various temperatures with my ETI Thermapen (and an additional – uncalibrated – ETI digital thermometer): The temperature reported by the Sous Vide Professional was consistently 0.5°C higher than that measured by the ETI thermometers. Should be no big deal, I thought, the Sous Vide Professional has an "offset calibration" feature to factor in a temperature offset of ±3.0°C.

Unfortunately, it wasn't as simple as that. While the manual describes the feature, it is out of date. To prevent accidental changing of the offset, a special power-off/power-on sequence has to be followed before the setting becomes active. Polyscience provided a bilingual (English/French) loose-page addendum to the manual describing the necessary steps. I followed them, but I still couldn't set offset.

After trying every possible interpretation of the described steps, I mailed Polyscience. They quickly replied and after some back-and-forth, it was determined that an error had crept into the addendum: instead of the power button, you have to press the menu button while connecting the unit to power. Here is the corrected sequence:

• Disconnect power cord
• Plug power cord back in while pressing the menu button
• Press menu button repeatedly until "offset calibration" is visible
• Change offset using up and down buttons
• Press menu button again or wait 10 seconds until the device shows the current and set temperatures again

[mkayahara]

Thanks for this. This is very handy information to have.

[Okanagancook]

I too have found Polyscience to provide very quick responses to questions you may have. You'll love yours.

[harryotto]

I think what's interesting about this thread is that it forgets one important point; thermometers are calibrated at temperatures thermal circulators never see - specifically 32F and 212F.

I've already had to calibrate* the offset of some Sous Vide Pro circulators but use the most accurate calibration tool in the world to do it; a CVS baby thermometer (not IR based).

Why?

First, they're deadly accurate in the 98-104F range.

Second, 100F is much closer to the temperatures we tend to circulate at.

The accuracy of a thermocouple tends to offset every 10 degrees or so in either direction. Although, the 32-212F calibration attempts to carve a linear graph to compensate, the baby thermometer technique works best as you can always get 100F direct from the tap.

*And it's always a good idea to "default" the unit before calibration. Great when the unit displays errors as well:

1. With the unit unplugged, press and hold UP ARROW while plugging in.
2. Release UP ARROW and press POWER button.

Edited by harryotto, 31 May 2012 - 02:09 PM.

[pep.]

I'm not quite sure what the point of your comment in this old thread is. The thread is not about what the proper protocol for calibrating thermometers is or what thermometer would be best. It's about the technical procedure to actually store that calibration in the device, nothing more and nothing less.

That aside, I re-checked after some time with a Greisinger GTH 175-Pt-K that was actually calibrated at 60 °C and the offset was correct.