# Identify unknown transistor (possibly faulty LM35 temperature sensor)

I have a transistor I know practically nothing about. It was included with an Arduino I got off the internet.

It has the words 36RA, LM35, and DZ on the flat side of the plastic. I have a digital multimeter with a function for measuring hFE, but I don't have access to the data sheet that would supposedly tell me what reading I should get because I don't know the model code or manufacturer. The symbol/function for testing diodes is on the 2K$\Omega$ function.

I have this data from experimenting:
(With flat side of plastic facing me)
Resistance between central pin (black probe) and left pin (red): 1.307k$\Omega$
Resistance between central pin (black) and right (red): 0.873k$\Omega$
hFE value for NPN with transistor on CBE: 25
hFE value for NPN on EBC (backwards): 295
hFE for PNP on CBE: 289
hFE for PNP on EBC : 24-25
hFE for PNP on ECB: fluctuates between 0 and 22
hFE for PNP on BCE: 135

In all measurements not stated the value was infinity or there was no response.

I'm a beginner at electronics (in case it wasn't evident).

Are you sure this is not the LM35 temperature sensor? A TO-92 doesn't automatically mean transistor. Here is a datasheet.

Hook up 5V to Vs pin and GND to GND. Measure voltage on Vout pin and see if it changes when you breathe on the sensor.

• +1 LM35DZ is the lowest (worst) accuracy grade and TO 92 case of LM35. – Spehro Pefhany Jan 2 '15 at 5:48
• Testing as of posting this comment. What's "TO-92"? – Arc676 Jan 2 '15 at 9:41
• @Arc676: en.wikipedia.org/wiki/TO-92 – Ignacio Vazquez-Abrams Jan 2 '15 at 9:46
• I followed the diagram on the 2nd page (TO-92 package) and wired it up to the GND and 5V on my Arduino. I connected a 10k$\Omega$ resistor to the output pin and added an LED. I measured the voltage across the resistor, but it didn't change when I breathed on it (2.7V). However, when I reversed the GND and 5V pins I got -2.4V. However, it's possible that I have a faulty temperature sensor instead of a faulty transistor. – Arc676 Jan 2 '15 at 9:59
• Or you may not have applied enough heat long enough. Try holding it between your thumb and index finger. – Ignacio Vazquez-Abrams Jan 2 '15 at 10:05

Given your added information in a comment above (you might want to add it to an edit to the question) that you're getting a 2.7V-ish reading when hooked up according to the data sheet, one might assume that the LM35 is damaged, however it's somewhat rare to have an intermediate voltage with a damaged chip.

Note that the proper output voltage for an LM35 is 0mV + 10mV/°C, so one would expect a voltage around the 200mV-250mV region.

If you have connected the chip exactly as below:

And it's still showing 2.7V-ish on the meter, then it's scuppered. However, if you've got a 10K to +5 or something like that, then it may be working but unable to control the output voltage (the LM35 is good at sourcing current, not at sinking current.