The Analog Of Things: LM vs TMP

Working with hobbyist projects invariably means working with a temperature sensor of some type, and at some point. The LM range of devices often comes into the mix, and interestingly there is the TMP range of devices.

The LM35 is functionally compatible with the TMP35, however, the LM and TP sensors are not the same and offer differing performances, voltage ranges, and resolutions.

The operational voltage range of the device depends on the type of application in which the device will function dependably. If the device can offer sustained performance at lower voltages then the device is user-friendly for battery applications.

The LM35 can be powered at 4V-30V

The TMP devices have a range of 2.7v to 5.5V

In most cases where an LM35 is used in a hobbyist project, the sensor is powered at 5Vdc, which is similar to the TMP 5.5V. In both cases, the sensors are good choices for a battery-powered application.

The LM35 has a slightly higher temperature range at -55'c to 150'C and is more accurate to +- 0.5'C.

The TMP36 has an accuracy +- 2'C, with a temperature range of -40'C to 125'C.

In both cases, the temperature accuracy is 10mV/'C.

At 25'C. the LM35 would produce an output of 250mV

At the same 25'C, the TMP sensor has an output of 750mV so ideally some mathematics needs to be applied to come to a converted temperature which a PIC Analog input can read and convert to a digital value.

The discussion is comprehensive, however, we have established that the LM35 would be the simpler, easier device to use in a project. We will take a closer look in an upcoming installment of how to implement a sensor from the TMP range and put that question to some further discussion.