# Data logger component identification

I'm trying to reverse engineer an aging datalogger. Before building my schematic, I would like to identify all the components. There is one component that I can't seem to identify after many hours searching the web. (T1). Can someone identify what it is please?

P.s How do you post a picture, sorry I'm new to the site.

Data Logger T1 component verification http://imgur.com/gallery/9RIDXmV

• T1 is more likely a designator, not a part number. Do you have a picture? Feb 9 '16 at 23:13
• Upload it and post a link -- we can edit it in Feb 9 '16 at 23:22
• Thanks for the quick reply. Yes I have a picture but I don't know how to add it. Can you help? Feb 9 '16 at 23:23
• @DavidRoberts: There is an "insert picture" button at the top of the post editor. If you don't have enough rep, upload the picture somewhere (imgur, for instance), post a link in the comments, and someone can help add it to your post. Feb 9 '16 at 23:29
• Are there similar looking components with T2, T3, etal designators? Also, can you get us closer photos of T1? Feb 10 '16 at 1:00

It is almost surely a thermistor intended to measure the PCB temperature. Here is a similar type.

Aside from the resistance at the reference temperature, thermistors come in different '$\beta$' values so try not to damage it- finding an exact replacement may be troublesome without info from the manufacturer.

• Thanks Spehro. After looking at the component under a magnifying glass I noticed there is 4 colour hoops brown, Green, orange and gold. Just like your picture. I think you have cracked it!! With the colour code I should be able to identify the value should I not hence I should be able to order an exact replacement? Feb 10 '16 at 18:31
• @DavidRoberts these colors mean 15K (they are read starting from the legs). Here is one like it (Spehro's link shows the wrong picture for the described product), but as he says, the nominal value doesn't define everything you need to know about it. You can try to replace it, but it may not be exact. Feb 10 '16 at 18:42
• Hi Oleksandr R thanks for the comment. What other characteristics do I have to look into. Will they have a negative effect on how things work? Could it cause damage to adjacent components. If I simulate the schematic using a schematic editor will it flag up the incorrect use of the component. Feb 10 '16 at 19:28

It's clearly not a conventional capacitor, since a neighbor is identified as C18. Since this is a data logger, and may be connected to who-knows-what, the component may be a transient voltage suppressor (TVS), the most "generic" variety being Transzorbs. Identifying this as Txx would make a good deal of sense.

In cases like this, I advise against getting too compulsive about identifying all the components before recreating the schematic. It often helps in identifying a component if you can see how it fits into the rest of the schematic.

• Yup, draw the schematic with it as "t1 (unknown?)" and this becomes a lot easier to answer in most cases. Feb 10 '16 at 0:51
• Or a thermistor... particularly in a datalogger. Feb 10 '16 at 1:48

If its a capacitor, you need to unsolder it from the board and measure it. The question is, what is it's use? Usually capacitors have two uses:

1. Power capactiors - if its connected to vcc and ground (you can kind of ohm out the pins to find out what its connected to, keep in mind the capacitor will try and charge during this time so you will have to wait until it charges to get a good ohm reading (thats why you need to take it off the board to measure it)) If it is indeed a power cap, that makes your life super easy, you just need to go equal to or greater than on the value.
2. Filter capacitors - This is usually also going from ground to somewhere on the analog signal chain, connecting with a resistor that is in series on the analog signal chain. Usually used to make a low pass filter (esp on a datalogger, I can't see why you'd need a high pass, if your measuring DC). You'll need to figure out where the pole is on the filter and what makes sense (were they trying to filter out frequency before the ADC?) and you will proabaly need an exact value.

If the capacitor isn't too small (under 10nF) you can measure it with a decent meter. If not you could also take it off the board and run a square wave into it with a resistor of your choice and measure the time constant of the "step input" from the square wave. If you have to repeat this with different resistors and take the average and you should be able to measure it quite well.

• Not "for sure" at all. Feb 10 '16 at 0:50
• @laptop2D: The capacitor on the left of the photo is named 'C18'. Why would that be marked with 'T1'? More likely a thermistor. Feb 10 '16 at 8:31
• If its a thermistor, take it off the board and plug it into a meter in ohms mode. Then put your hand on it to change the temperature, you should see a change in resistance. I don't know why they would want to put a thermistor in the middle of the board, they could do some temperature correction, but I would put it closer to the amps. I've seen a lot of designators that don't mean a thing on PCB's sometimes you decide to put a transistor in and you put a cap in instead. Feb 10 '16 at 18:15
• Yeah, not for sure at all Feb 10 '16 at 18:18