Where should I mount my thermostat's probe?

IMPORTANT: If you are experiencing an overheating condition with a multioutlet thermostat such as the Herpstat 2 or Herpstat 4 this is typically caused by the probes being mismatched with the wrong AC outlets. For instance the #1 probe inserted in the #1 cage who's heating device is plugged into the #2 AC outlet. Or the #1 probe inserted into the #2 cage. Anytime the probes are not joined with their corresponding AC outlets an overheat condition typically happens. Carefully double check all wires to make sure they connected directly. If a problem still exists then check for a hardware failure using the information from this article

Where should I mount my thermostat's probe. 

Probe placement is typically the most important factor in getting an enclosure to regulate. If you have a brand name manufactured rack or enclosure you should ask that company first for their recommendation. While Spyder Robotic's have some general recommendations every enclosure is different and may require some experimentation to fine tune the regulation. 

Rack Systems:
Note: Rack systems will always be hotter on the top shelves than the bottom shelves due to heat naturally rising. When setting thermostat temperatures based off of the middle shelves of racks be sure to check your top shelf temperatures to be sure they are not too hot for the animal.

1. MOST COMMON METHOD.  Mount the probe directly on the heat source of a middle shelf. With this method you are controlling the temperature of the heat source and not the tub temperature directly. 

The probe wire is out of reach of the animals. 

On initial regulation the temperature displayed on the thermostat may overshoot since the probe is directly on the heat source. The temperature in the tubs will be much cooler and it requires the use of a seperate thermometer inside the tubs to see what the animal is experiencing. You will need to set the temperature higher than the target tub temperature while watching the temp from the seperate thermometer and adjust the thermostat temperature until your desired tub temperature is reached. As room temperature changes, the temps in the tubs will be affected more because the temperature of the heating source will change less and that is what the thermostat is controlling. 

2. Mount the probe inside a tub in a middle shelf closest to the heat source. With this method you are controlling the tub temperature directly. 

Since the tub temperature is controlled directly you can set the thermostat to temperature you want your animal to experience. Seperate themometers are not needed. As room temperature changes the thermostat can self adjust to keep the tub temperatures more accurately. 

If the tub that contains the probe is left pulled out the rack can overheat trying to compensate since the probe is no longer sensing heat. Requires making sure the probe is secure enough so that the animal cannot dislodge it. Some use an empty tub for this but that results in lost rack space. 

Enclosures Heated From The Top: 
While many models of herpstat do include a BASKING ASSIST mode required to work with basking lamps we do not recommend lamps in general for regulated heating control.  If using a heating device such as a basking lamp or ceramic heat lamp the probe must drop through the ceiling right next to the lamp shade with the probe tip dangling in the air not touching anything about 3-4 inches away from the bulb.   If using a radiant heat panel mound the probe directly flat to the middle of the panel with a heat resistive tape like a good quality duct tape.  The tape should cover the probe tip securing it to the panel.  The floor temperature will be cooler than what the thermostat is controlling. Top heated enclosures require the use of a seperature thermometer to measure the floor temperature. You will need to set the temperature higher than the target floor temperature while watching the temp from the seperate thermometer and adjust the thermostat temperature until your desired floor temperature is reached. Do not increase the temperature on the thermostat beyond what is safe for the animal.  

Enclosures Heated From The Floor: 
1. Put the probe inside the enclosure and secure it on the floor over the area where the heating device is. Do not mount the probe on the bottom of the heating device under the enclosure. This will typically result in overheating the enclosure floor because the heat will rise an and the probe will not sense this heat. 
2. Sandwiching the probe between the heating device and the bottom of the enclosure may work but will require you to set the temperature slightly higher that the temperature you want to see inside the enclosure on the floor due to heat loss from the floor material. 

Situations That Can Cause Regulation Problems: 
Do not use water bottles in incubators which can cause thermostats to overshoot the target temperature due to the water emitting heat after the thermostat has turned power off to the heating device. Do not apply aluminum tape directly to the probe tip. This will cool down the probe tip causing invalid readings. 

The information in the article is the opinion of the author and is to be used at your own risk. Spyder Robotics assumes no responsibility for the accuracy or use of this information.

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