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Thread: Heatermeter weird issue

  1. #11
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    since you have a connector on the thermocouple sensor, just disassemble and make sure the connections are good and where they strip the outer jacket back, they did not damage the insulation on the thermocouple leads where the shield stops and the couple leads emerge. I have had to carefully remove some outer jacket and make new connection when I have found this issue. Also make sure the thermocouple wires that are clamped in the connector are using all the wire. Clamping only a small portion of the wire can cause problems since the couple is generating a voltage. This can increase the issue with noise.

  2. #12
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    Good points Gary....
    If the outer shield is touching the bare TC wire I could see that causing this issue, and loose tc wires in the connector could do the same. Only thing is, I think he said he tried a couple TC's.
    I have to say it again for others who may read this thread, I always verify the TC's that I purchase are the ISOLATED type, I find them to be much less susceptible to these sort of issues and less noisy in general. The Thermoworks specs will tell you if they are isolated type, and when I bought generics on Amazon or Ebay I just emailed and asked if isolated before I purchase if it isn't noted in the listing.
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  3. #13
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    Ok, did some checking.
    First the download of the noise graph software on a good and a wrong one:
    Good one without touching wire:

    Good one with touching wire:

    Wrong one without touching wire:

    Wrong one with touching wire:

    I have checked the temparature probe as well and there is a connection on the shield and the inner wires... so its not insulated

    Having said this... the correct units do show effects when touching the wire (see above) but still function as normal.... why don't they all?

  4. #14
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    maybe flux on the board around the TC amp?
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  5. #15
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Quote Originally Posted by Dennis R View Post
    Having said this... the correct units do show effects when touching the wire (see above) but still function as normal.... why don't they all?
    Huh, that is definitely interesting. The first image is how HeaterMeter expects them to look. The second is what it normally would look like if the power supply / power source wasn't great and you can see the curve is a ~50Hz sine wave matching the input power frequency. You can see that it is still centered around the right value but slightly off since the sample period includes slightly more than one full period. That could be addressed by using the "A/C input line noise filter", but obviously would be better to find a root cause. The challenge being that the full range of that graph is just 13mV (0.013V) peak-to-peak so it isn't some giant error that would be easily detected.

    The others seem to always be showing a similar wave but not exactly matching the input AC voltage wave which is just boggling. You start by testing to see if it is a problem with all analog inputs or just the thermocouple by using a 1k resistor in place of a probe on one of the thermistor inputs. If you just tack a 1k resistor to the side pin on the mono jack and the pin on the board edge (with no probe plugged in), it should read 337.7F/169.8C. You could also put it in the J2 header between the pin you're testing (1-3) and GND. On the noise graph, the numbers on the right indicate which input it is sampling. 5 = Pit, 4 = FOOD1, 3 = FOOD2, 2 = FOOD3, 0 = BUTTONS. It also takes up to 10 seconds for the graph to cycle to the next update, so expect nothing to immediately happen when you click the number.


    The scale of the graph will likely be 1/3rd the size, but given how giant the wave is on the bad ones I think it will still be obvious if it is a problem with all inputs or just the thermocouple and we can decide which direction to look once we know.
    I'm that HeaterMeter guy what ruins everybody's free time.

  6. #16
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    I will get a new 1K resistor.. I seem all out.
    I tried to tag a SMD 1K to 2 wires but that really didn't work
    A 220 ohm resistance gave 396 deg on all probes:

    When I put a ET-73 probe in, the temp is fine (20degC) on the probe jacks... just really not on the TC..

  7. #17
    TVWBB Honor Circle Bryan Mayland's Avatar
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    The value doesn't matter really, we just need something that is low resistance, 1k or less, but not so low that it gets rejected by the sanity filters in HeaterMeter. Looks like you picked a winner right on the low end and the good news is that the issue doesn't seem related to the microcontroller's ability to measure the analog values properly, since you've got a perfect looking noise graph there.

    But now the problem is I'm not sure where to look from here. Have you already tried reflowing the solder on the thermocouple amp legs? The only thing beyond that I can think of is check the 100uF capacitors on the board to make sure they have a good connection as well since it seems that somehow the power has that mains voltage wave on it still, even if it is just a new millivolts.
    I'm that HeaterMeter guy what ruins everybody's free time.

  8. #18
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    I resoldered all items on the TC part, including the capacitors and the legs of the amp.
    The thing that is most worrying to me is that, of the 3 units with an issue, the graphs are exactly the same as a baseline as well as when I touch the wire.
    This seems to me that the issue is identical as well...
    Is there any way to measure the components themselves to exclude the possibility of having a bad batch of resistors somewhere?

  9. #19
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    In most cases you wont be able to measure components value while in circuit due to other devices connected to the circuit, the best you could do is compare readings on the bad unit with readings on a good unit (with power OFF), noted differences might help point you in the right direction.
    Have you already tried cleaning the board (TC Amp) with alcohol and a soft brush? Excess flux on the board can make the probes wonky at times....
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  10. #20
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    I was just doing exactly that while I received the message of the topic response
    This is difficult to explain but I hope I can make sense:
    left bottom (10k) is measurable and gives 10k as reference
    left top (10k) as well
    top center (1k) is 1k and below (10n) this is measured at 1100.
    The top right (10n) and middle right (1n) give very high numbers (16M)
    the one underneath (0,1u) the amp is unreadable and even gives negative readings sometimes.

    Having said its pretty difficult to get proper readings...
    The biggest difference that I could find in the readings is the upper left (10k) which measures 1k...
    I really don't think I soldered the wrong one but would I measure a correct value on this resistor when connected?
    Or is it another item nearby that influences it directly and can that one be the issue.

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