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Apogee Instruments offers three styles of thermistors and the most accurate PRT commercially available.


ST-100 Thermistor
The ST-100 is a high accuracy thermistor (± 0.1 C from 0 to 70 C), mounted in a waterproof housing, designed for continuous measurement of air, soil, or water.


Size Comparision


ST-110 Thermistor
The ST-110 is a high accuracy thermistor (± 0.1 C from -40 to 60 C) designed to minimize solar load and thermal conduction. White heat shrink is used on the cable behind the thermistor to reduce solar load. Constantan wire is used to minimize thermal conduction down the wire towards the thermistor.


ST-150 Platinum Resistance Thermometer (PRT)
The ST-150 is a 1/8 inch, Class A PRT with an IP67 rating. White heat shrink is used on the cable behind the PRT to minimize heat transfer to the sensor. PRT sheath dimensions are 3 mm diameter and 56 mm length, minimizing thermal mass.

ST-200 Fine Wire Thermistor
The ST-200 is an accurate (± 0.2 C from 0 to 70 C) fine wire (0.45 mm tip, 0.15 mm wire) thermistor designed for measurement of delicate surfaces or small samples with a fast response time, less than 1 second.


ST-300 Platinum Resistance Thermometer (PRT)
The ST-300 is a high accuracy PRT (1/10 DIN) designed to minimize solar load and thermal mass. White heat shrink is used on the cable behind the PRT to reduce solar load. PRT sheath dimensions are 3.18 mm diameter and 63.5 mm length, minimizing thermal mass.

CS240 Back-of-Panel Temperature Sensor
The CS240 is a surface mountable PT1000 Class A PRT designed to measure back-of-panel temperature with the highest accuracy. The PRT is housed inside a rugged, self adhesive aluminum disk designed to withstand harsh environments and promote heat transfer from the panel surface. Kapton tape is required for cable strain relief and to fasten the CS240 to the back of a solar panel.


Warranty and Support
All Apogee products are backed by an industry-leading four year warranty and outstanding customer support.


Need help choosing a sensor?

  Technical Information
Technical Information
Find knowledge base articles, manuals, FAQs, technical support, and more.
+ How accurate are Apogee temperature sensors?
Measurement Uncertainty
ST-100   ST-110   ST-200   ST-300
0.1 C (from 0 to 70 C),
O.2 C (from -25 to 70 C),
0.4 C (from -50 to -25 C)
0.1 C (from 0 to 70 C),
0.15 C (from -35 to 0 C)
0.2 C (from 0 to 70 C),
0.4 C (from -50 to 0 C)
0.1 C (from -40 to 60 C)
+ Does the ST-100 have NIST traceability?
All thermistors are measured for accuracy in specially designed constant temperature baths that are directly traceable to the National Institute of Standards and Technology (NIST). The overall measurement system uncertainty or all the bath and measurement allowances combined for error is typically less than 0.01 C and completely traceable to National Standards.
+ Can I use the temperature sensor with a voltmeter?
Yes with a voltmeter that measures resistance. Once you measure the resistance across the thermistor, that resistance corresponds to a temperature a table with the corresponding temperatures and resistance can be found here. The correct thermistor wires to measure on the ST-100, ST-110 and ST-200 are red and black.

spec sheets
Specification Sheets




Air Temperature Measurement Sensors

Lecture 1-Air Temperature & Humidity



For non-contact temperature measurements see our infrared radiometers