can the thermostat - 3NT01L-H7895 measure contact surface or/and ambient temperature? If they can measure both, any installation consideration we have to make? As well: a supplier recommends Watlow ST-207E which sounds similar to 3NT01L-H7895, but 10 times expensive. Do you know why?
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The 3NT01L-H7895 Sensata Technologies is designed for direct contact measurement. A typical installation clamps the sensor to a tube such as the suction line of a refrigeration unit.
The data sheet mentions a snap action mechanism with the ability to switch up to 10 A @ 240 VAC (non-inductive).
Based on this description, I would expect the sensor to work equally well clamped or unclamped. There appears to be a wide hysteresis (temperature difference between activation and deactivation). Consequently, we shouldn’t expect the sensor to toggle excessively (chatter) and any self-heating should be minimal.
As for the Waltlow device, I am uncertain. The sensors appear to be designed to operate in the same harsh, humid, and condensing environment. Both have similar specifications and tolerances as described in the Standard Temperature and Tolerances section of the datasheet.