PT100 amplifier board - redaings seems to be 30 degrees below

[tony449777]

@phaedrux

R1 200.2
R2 200.2/3

[Phaedrux]

@tony449777 They appear to be exactly half of what they should be...

[tony449777]

@phaedrux I wonder how that could happen? I believe I got this daughterboard from Filastruder. It was purchased a while ago, but never used until this build.

[dc42]

@tony449777 the multimeter may give the wrong (lower) resistance readings, depending on what voltage it uses to measure resistance. If it was previously working then the resistors should be OK.

[tony449777]

@dc42 I’m using a Fluke. I have 3 others. I’ll try them all. However, how would we ever be able to come up with a reference for resistors if all multimeters give us such a diverse readings?

[tony449777]

@dc42 I can’t attach a picture, it will not let me however I can tell you R1 is marked”102” while R2,R3,R4 are all marked “201”

[tony449777]

On my precision bench meter both resistors measure R1-199.50 and R2-199.52

[tony449777]

I also have 3 PT100 cartridges in the same room measuring within 1° of each other. By that I mean looking at a PT 100s resistance table and measuring each one’s resistance, according to the table they are within 1° of each other.

[tony449777]

Also curious, if the channel 1 on the daughter board is “spi.cs1”
And you have one daughter board with the two ports, then is the second port for the same card “spi.cs2”?

[tony449777]

This post is deleted!

[dc42]

@tony449777 said in PT100 amplifier board - redaings seems to be 30 degrees below:

@dc42 I can’t attach a picture, it will not let me however I can tell you R1 is marked”102” while R2,R3,R4 are all marked “201”

Why can't you attach a picture?

Do both channels give the wrong reading when you connect the 100 ohm resistor to each in turn?

[dc42]

@tony449777 said in PT100 amplifier board - redaings seems to be 30 degrees below:

Also curious, if the channel 1 on the daughter board is “spi.cs1”
And you have one daughter board with the two ports, then is the second port for the same card “spi.cs2”?

Yes.

[tony449777]

@dc42 yes

[tony449777]

@dc42 I’m using the phone application. Every time I try to attach a picture it just says undefined.

[dc42]

@tony449777 it's easier from a PC, you can just drag and drop a .jpg file into your post.

[tony449777]

@dc42 Update. Switched out the daughter board for another one I purchased from filastruder and it works fine. It must be the board.

[Phaedrux]

@tony449777 said in PT100 amplifier board - redaings seems to be 30 degrees below:

I believe I got this daughterboard from Filastruder. It was purchased a while ago, but never used until this build.

How long is a while ago?

[c310]

@dc42 my 2nd channel died :I( i will be replaceing the chip, on the way want to check other parts. there are 2 pairs of capacitors - c1/c2 + c5/c6 what its default capacity should be?

also there is small black SMD element in between C1 and R1. what is it? what are the parameters?

many thanks!

[T3P3Tony]

@c310 the schematic for the board is here:
https://github.com/Duet3D/TempDaughterboards/blob/master/MAXTempRTD/MAXTempRTDv1.1.pdf

I assume you are refering to the inductor L1:


two screen shots depending on the version of the PT100 db you have.

it is an inductor such as LB2012T101K

[c310]

@t3p3tony said in PT100 amplifier board - redaings seems to be 30 degrees below:

LB2012T101K

thank you @T3P3Tony !!!!