Hey folks,

I've made a adjustable duel thermometer using a lm393n. I got a pack of thermistors but they don't come protected against liquids... is there any kind of resin I can dip them in without it changing the sensitivity of the thermistor to much?

Thanking yourselfs!

 

You know that an LM393 is a dual comparator, right?

You could use conformal coat to protect them, or clear lacquer. It will reduce their sensitivity a little, but not too much. They simply won't respond quite as quickly.

 

I dipped one in clear epoxy and then put shrink tubing on it (and the cable it was attached to) before the epoxy hardened. That slowed the response time down from a few seconds to most of a minute, but it was for a water bed heater where time is considered in terms of hours.

 

I think maybe the lacquer might do the trick then... if I use one thats already incased it makes the relay judder for several seconds ...even if I adjust the hysteresis. But it seems to work fine with one that isnt incased!

 

This is a perfect example of, "post a schematic to get good answers quickly".

 

The problem with your "juddering" is because you do not have hysteresis in your comparator circuit.

If you would post a schematic diagram of your circuit, we could tell you how to fix it to avoid the "juddering".