Blichmann Brewmometer Problems

This my second time using the brewmometer on my mash tun and both times I've had problems with inaccurate readings. I mashed in at 150F and everything was fine - my digital probe matched the brewmometer. The problem is that the brewmometer's reading drops like crazy during the mash. Here I am 30 minutes into the mash and it is reading 134F, while the digital is still reading 149-150. The same thing happened last time.

It was calibrated, so what could be the problem?

We need more information. What type of mash tun are you using? Is it a cooler or a kettle? Are you direct firing the MT? Are you circulating the wort? Where is the Brewmometer located on the MT? Where is the probe for the digital positioned?

The mash will tend to stay warmer at the top than at the bottom. It will also be hotter in the center than at the outside edges. The differences are usually larger with a kettle type MT than with a cooler. The grain bed will never be of a completely uniform temperature. The bi-metal dial type thermometers are notoriously unreliable. Even the relatively expensive ones can be problematic. Some home brewers report no problems with them at all, but I gave up on them completely quite a while ago. I went with a digital thermocouple traceable thermometer that I like a lot and it's proven to be accurate and reliable. My expensive dial thermometer would be off as much as 10 degrees even after repeated calibration attempts. The error was not consistent across the scale which rendered it completely useless in my brewery. Your dial thermometer may have been damaged. They are rather fragile instruments even though they don't appear to be. If you bump against the probe when stirring the mash, it can damage it. Dropping it or exposing it to very high temperatures can also mess it up. Once damaged, recalibration often won't fix it. A bent probe usually spells doom for those things.

It's a converted keg with a stainless false bottom. I've got it on a 3-tier gravity fed system. I direct fire to heat the strike water but only do single infusions so I don't recirculate. I've brewed on it dozens of times b4 getting the brewmometer and it's always held the temp within 3 degrees in the summer time. There are differences in temp throghout the grain bed but when I tested with 2 different thermometers I took the temp right at the brewmometer probe. The brewmometer is mounted about 3 1/2 inches off the floor of the keggle.

Crappy to hear this $40 thermometer is less reliable than my $7 Wal-Mart one. I'll have to check it closely for damage after this brew day. It's so new I really don't think anything has happened to it, unless bumping it with my stirring spoon could really screw it up. If so that's BS b/c it's pretty much impossible to not bump it at all.

OK, well it sounds like you've checked it properly. Has the Brewmometer been exposed to excessively high heat maybe? What type of burner are you using? The big banjo type burners usually require you to protect thermometers, valves and hoses with heat shields of some kind. I ruined my dial thermometer with my mash rake although it showed no outward sign of damage at all. At least that's what I think caused it to go bonkers on me. I did not bump it very hard at all, but I did bump it repeatedly while stirring the mash.

I notice the same thing with mine, I mash in a boilermaker pot and direct fire and recirculate. When I am not recirculating I notice that the brewmometer temps start dropping quickly. I chucked this up to the probe only being 2 inches into the pot and the walls cooling faster than the core of the mash where I took the digital readings. I just recirculate and take multiple readings with different thermometers to make sure I am in the ballpark. I might look into using a fireproof insulation, but that seems like more of a pain than its worth when I can just throw a little heat to the bottom and pump it around to the top.

Catt22 said:

OK, well it sounds like you've checked it properly. Has the Brewmometer been exposed to excessively high heat maybe? What type of burner are you using? The big banjo type burners usually require you to protect thermometers, valves and hoses with heat shields of some kind. I ruined my dial thermometer with my mash rake although it showed no outward sign of damage at all. At least that's what I think caused it to go bonkers on me. I did not bump it very hard at all, but I did bump it repeatedly while stirring the mash.

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Hmm maybe it is the heat. I did notice on my brewmometer on the boil kettle that it got hot to the point I couldn't hold my finger on the outside. They are in the same place so I'm sure the MT one got hot as well. But can it really not handle that? It's not a banjo. I'm pretty sure it's Bass Pro Shop brand but I don't know the BTU rating. What's strange is that it is spot on when I'm heating the strike water (also when the temp is the hottest since the burner is on). It's only a few minutes after the mash starts that it drops like a rock. Maybe it really is just from the outside cooling as RiverCity said. But if it is taking the temp from the end of the probe, which I believe it should, then there is no way the readings are accurate.

RiverCityBrewer said:

I notice the same thing with mine, I mash in a boilermaker pot and direct fire and recirculate. When I am not recirculating I notice that the brewmometer temps start dropping quickly. I chucked this up to the probe only being 2 inches into the pot and the walls cooling faster than the core of the mash where I took the digital readings. I just recirculate and take multiple readings with different thermometers to make sure I am in the ballpark. I might look into using a fireproof insulation, but that seems like more of a pain than its worth when I can just throw a little heat to the bottom and pump it around to the top.

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Thanks for sharing your experience. As I mentioned above it could be a result of cooling on the outside, but it said the temperature dropped about 25 degrees over the 60 min mash. Even the outer edge of the pot read within 3 degrees of my target temp when using a digital.

It's still useful for heating the strike water because it seems to be accurate for that, although I know I'll double check it which defeats its purpose.