How trustworthy are the thermostat temps?

[Kaorte]

I have a johnsons controls thermostat hooked up to both my snake tubs. I have it set for 93*. I have the probe taped to the flexwatt outside the tub. I have been measuring temps all day and I keep getting crazy readings. I have used my thermometer with a probe inside the tub and it reads 85*. I use my temp gun (I am thinking its not very reliable :/) and it says 100* and the thermostat says 93*.

WHAT IS RIGHT??

[JeffJ]

I have a johnsons controls thermostat hooked up to both my snake tubs. I have it set for 93*. I have the probe taped to the flexwatt outside the tub. I have been measuring temps all day and I keep getting crazy readings. I have used my thermometer with a probe inside the tub and it reads 85*. I use my temp gun (I am thinking its not very reliable :/) and it says 100* and the thermostat says 93*.

WHAT IS RIGHT??

surface temp is always different then ambient. even probes cannot get a 100% true surface temp reading.

i notice the same thing but, believe me the temperature gun is accurate. i saw a thread about htis 2 weeks ago as well.

[Kaorte]

surface temp is always different then ambient. even probes cannot get a 100% true surface temp reading.

i notice the same thing but, believe me the temperature gun is accurate. i saw a thread about htis 2 weeks ago as well.

I am not asking if the temp gun is right. It gives me erratic readings, and I don't trust it. I am asking how reliable the thermometer built into the thermostat is.

[DutchHerp]

The thermometer built into the tstat is usually not very accurate. I'm not sure about Ranco's, but even my Herpstats don't give the exact reading.

The probe of the thermostat does not measure the exact temperature; it also gets some ambient temps on it.

That, and probably the fact that the Ranco is made for controlling temps and keeping them in a specific range instead of giving you the exact temperature, is probably why you shouldn't trust the temps on the tstat.

[JeffJ]

I am not asking if the temp gun is right. It gives me erratic readings, and I don't trust it. I am asking how reliable the thermometer built into the thermostat is.

its reliable to its specs. but the probe is meant to meter ambient temperature. not surface. this is where the discrepancy is arising. its like comparing apples to oranges. surface temperature will always be different then the heat radiated from it.

[Kaorte]

its reliable to its specs. but the probe is meant to meter ambient temperature. not surface. this is where the discrepancy is arising. its like comparing apples to oranges. surface temperature will always be different then the heat radiated from it.

a 15* difference is a bit much though, don't you think?

[JeffJ]

a 15* difference is a bit much though, don't you think?

depending on how close you hold it will affect the reading too. the closer you hold it the finer the surface area it reads from if i hold it 1/2 inch from the substrate compared to an inch i can usualy see 1-2*f difference as well. 15*F might be a little bit extreme but i could be wrong could be 100% normal. i dont get that huge of a difference. but its at lease 8*f difference for me

[Jsh]

My temps read:

Herpstat 99

acu-rite:
hot side 92
ambient 81

temp gun:
hot side 93
cool side 80
snakes core between 83-89

Took 3 days to get everything as I like it! Pretty big difference between the herpstat and ambient tub temps. I was having sort of the same issues the first few days.

[Kaorte]

I am finding that the temps are higher than what the thermostat reads.
I guess I will just be fidling some more tonight.

[alohareptiles]

Just a thought is where is the probe located? Is it on the hot side or cold? Is it high or low? When my probe on my Ranco was high it caused the surface temp to be too low, but when I lowered the probe almost to the ground I was able to even out the ambient and also increase the surface temp...I notice mine off a good amount too, but all are within the accepted temps zones...And I have 3 cages hooked up to my Ranco...but I admit it is frustrating...