Reference Thermometers - Glass or Digital?

I've been working as a Manager with a new company at a small forgotten plant (I often say we're the forgotten step-child) within the company for almost two months now. And I discovered, to my horror, the other day that the glass reference thermometer that they have been using to do in-house calibration verification hasn't been actually NIST calibrated since the 80's. So, since the glass thermometer that we do have is in degrees C and we use both C and F in the plant I've started on a journey of glass - which corporate recommends - vs. the digital Aquatuff that I have a fondness for. 

 

Does anybody know if there is a preference among SQF/USDA/FDA/etc. for one over the other? This is assuming that if I were to get a new glass one it would be in F and I would get it and the glass C thermometer both calibrated yearly, while if I were to get a digital it would suffice for both F and C and would be the only thermometer calibrated yearly.

 

Thanks!

 

Sarah

Hey Sarah,

   Sorry to hear that your reference thermometer's last NIST calibration was in the 80s.

 

Either or is fine as long as you have a calibration policy.

 

So if you go the glass thermometer route as your reference, you just need one. Just convert C into F. Also, we're SQF certified and have an annual NIST calibration on this glass thermometer. This is what we do.

 

 But if you prefer digital thermometers, you can get an annual NIST calibration and verify the accuracy with the following instrument:

 

http://www.teltru.co...calibrator.aspx

 

And you would need to get this calibrated annually too.

 

Regards,

Bill

Hi Sarah,

 

Given a choice I would avoid having a glass thermometer in my plant as it is adding a preventable hazard. Plus as you say the digital thermometer can cover both scales.

 

Regards,

 

Tony

Hi Sarah-

     It is my understanding that certification of a digital thermometer is based on the combination of base AND probe, so the main reason that I continue to use a MIG thermometer is to avoid having to get the digital recertified if you have to change the probe for any reason - like a frayed cord. If you have a one-piece unit, I guess that is a non-issue...

We recently just got rid of our Standard glass thermometers and are switching over to a Digital Standard themometer which we will send out annually to be NIST certified. The pro's i see in this are: No worring about Mercury, No worrying about glass and No worrying about if someone is reading it correctly.

I ended up ordering the digital thermometer. As far as in-house calibration verification we use an ice bath (and boiling water if necessary, but the thermometers that are used for hot temperatures here are checked/sealed by the state) since it is cheap and practical. In the milk industry we verify thermometers far less than I would prefer - some are done every 6 months and others are once a year - so getting anything to aid in this just seems like a waste of money. I'm trying to get into a pattern of checking thermometers more frequently, but the person who was doing calibrations before I got here (on thermometers, anyway, another one does scales, and a third does pipettes... the split of duties here is strange) is excessively reluctant to either increase the frequency or to allow me to do it for him. And since I'm changing a lot around here I prefer to pick my battles. 

 

Concerning the need of re-calibration if you change the probe, I do believe that is true, but there really should be no need to have to replace the probe on a reference thermometer... or at least not frequently. To me, a reference thermometers sits in a cushy location until you pull it out to use it. If I were using it daily I could see how something could possibly go wrong but then the frequency that you use it could justify the cost to re-calibrate it. Where we will use ours so infrequently I'm not really concerned about that situation. It is a possibility that something could go wrong with the probe, but if we managed to go 30 years with the same glass thermometer I'm hoping that we can manage with a digital/plastic one. 

 

Thanks everyone for helping me out! Now if I could just manage to get rid of the non-shatterproof light bulbs in the plant...

I ended up ordering the digital thermometer. As far as in-house calibration verification we use an ice bath (and boiling water if necessary, but the thermometers that are used for hot temperatures here are checked/sealed by the state) since it is cheap and practical. In the milk industry we verify thermometers far less than I would prefer - some are done every 6 months and others are once a year - so getting anything to aid in this just seems like a waste of money. I'm trying to get into a pattern of checking thermometers more frequently, but the person who was doing calibrations before I got here (on thermometers, anyway, another one does scales, and a third does pipettes... the split of duties here is strange) is excessively reluctant to either increase the frequency or to allow me to do it for him. And since I'm changing a lot around here I prefer to pick my battles. 

 

Concerning the need of re-calibration if you change the probe, I do believe that is true, but there really should be no need to have to replace the probe on a reference thermometer... or at least not frequently. To me, a reference thermometers sits in a cushy location until you pull it out to use it. If I were using it daily I could see how something could possibly go wrong but then the frequency that you use it could justify the cost to re-calibrate it. Where we will use ours so infrequently I'm not really concerned about that situation. It is a possibility that something could go wrong with the probe, but if we managed to go 30 years with the same glass thermometer I'm hoping that we can manage with a digital/plastic one. 

 

Thanks everyone for helping me out! Now if I could just manage to get rid of the non-shatterproof light bulbs in the plant...

 

Thank you for the update, Sarah!