Adc pin getting different results in during charging of board.

RE: Adc pin getting different results in during charging of board.

Karl Ylvisaker — Wed, 31 Aug 2022 07:16:30 GMT

Hello Zuhaib,

This case is over 2 years old so I think the chance for an answer from the original poster is very low. If you require technical support, or have any issues with your setup then I highly recommend that you create a new ticket to ask about this instead :)

Please do not hesitate to open a new ticket for your inquiry.

Best regards,
Karl

RE: Adc pin getting different results in during charging of board.

zuhaib — Mon, 29 Aug 2022 10:18:20 GMT

can you let me know about the correct schematic

RE: Adc pin getting different results in during charging of board.

Karl Ylvisaker — Tue, 08 Sep 2020 08:08:14 GMT

[quote user="jpatel"]Sorry for the late. Now, I am getting value from ADC.
The problem was the wrong Schematic.
So, I have discussed with the client and after providing a new schematic In that, I am able to read the value.[/quote]

No worries at all, I am happy that you were able to resolve your issue!

Please do not hesitate to open a new ticket if you should encounter any issues or questions in the future.

Good luck with your development!

Best regards,
Karl

RE: Adc pin getting different results in during charging of board.

jaimin — Tue, 08 Sep 2020 04:28:58 GMT

Thanks, Karl,

Sorry for the late. Now, I am getting value from ADC.
The problem was the wrong Schematic.
So, I have discussed with the client and after providing a new schematic In that, I am able to read the value.

RE: Adc pin getting different results in during charging of board.

Karl Ylvisaker — Wed, 19 Aug 2020 07:31:01 GMT

Hello again,

[quote user="jpatel"]Band has single NTC sensor with 2 input NTC+ and NTC-. I am trying to read both pin based on analog pin Ain1 and Ain2 and difference out that value.

In that has this NTC :http://www.semitec.co.jp/english/products/thermo/thermistor/et/#anc-et
part no: 503ET-3H[/quote]

Thank you for clarifying.

[quote user="jpatel"]I have brought band from one of company. with that provided firmware sensor is works .So, i don't think hardware connection issue.But it's maybe possible configuration of the SAADC issue.[/quote]

This sounds like it could indeed be the SAADC configuration who is wrong, and not the hardware connections.

[quote user="jpatel"]Ok i wil check and update you results.I will check one by one channel voltage and based on that will verify resistance value.[/quote]

Great!
From the datasheet you linked it seems like you should be able to see a voltage drop corresponding to ~50k Ohm resistance at 25 C if the raw measurements are correct.
I look forward to hearing the results of the test!

Best regards,
Karl

RE: Adc pin getting different results in during charging of board.

jaimin — Tue, 18 Aug 2020 16:40:16 GMT

[quote userid="87869" url="~/f/nordic-q-a/64854/adc-pin-getting-different-results-in-during-charging-of-board/265149"]Just so I have understood you correctly: are you using two NTC with single ended inputs, or a single NTC sensor with differential input?
I.e are you looking at the difference in temperature between two points, or are you attempting to measure temperature at two different locations?[/quote]

Band has single NTC sensor with 2 input NTC+ and NTC-. I am trying to read both pin based on analog pin Ain1 and Ain2 and difference out that value.

In that has this NTC :http://www.semitec.co.jp/english/products/thermo/thermistor/et/#anc-et
part no: 503ET-3H

[quote userid="87869" url="~/f/nordic-q-a/64854/adc-pin-getting-different-results-in-during-charging-of-board/265149"]So, it seems either the hardware connection to the NTC is not correct, or the configuration of the SAADC to measure the NTC is incorrect.
Do you have the datasheet of the NTC sensor, so that you may verify that connections between your sensor and your nRF is correct?[/quote]

I have brought band from one of company. with that provided firmware sensor is works .So, i don't think hardware connection issue.But it's maybe possible configuration of the SAADC issue.
Yes,I have datasheet.

[quote userid="87869" url="~/f/nordic-q-a/64854/adc-pin-getting-different-results-in-during-charging-of-board/265149"].e if you on channel 0 sample close to 3 V, then the thermistors resistance must be zero which corresponds to some reasonable temperature level. These are all random numbers, but could you see if you are able to read this out, to verify whether the results coming out of the SAADC are correct or not?
If we could verify that these results are reasonable, then we may move on to debugging the Steinhart forumla implementation.[/quote]

Ok i wil check and update you results.I will check one by one channel voltage and based on that will verify resistance value.

Thanks.

RE: Adc pin getting different results in during charging of board.

Karl Ylvisaker — Tue, 18 Aug 2020 14:15:28 GMT

Hello,

[quote user="jpatel"]No, Karl, I have just searched in the browser and found a formula to read the NTC temperature using steinhart and I have applied that. Below link for formula.[/quote]

I see. I am not familiar with this module and repository, but it seems to account for the resolution of the SAADC, so I suppose it is meant to receive raw saadc output.

[quote user="jpatel"]Ok but, I have check AIN1 and AIN2, raw AADC value not getting vary based on temperature.
I have tried to print Buff[0] and Buff[1] raw value of SAADC for AIN1 and AIN2 but that value not changed. I provided high or low heat using flashlight on the sensor to check the raw value of Ain pin but that not changed getting fixed value buff[0] = 700 and buff[1] = 350 around values.[/quote]

Just so I have understood you correctly: are you using two NTC with single ended inputs, or a single NTC sensor with differential input?
I.e are you looking at the difference in temperature between two points, or are you attempting to measure temperature at two different locations?

[quote user="jpatel"]So, I think ADC was not configured properly. To verify that, I have just change Ntc to battery voltage AIN pin and In that, I have to see Raw value changed based on increased or decreased battery voltage. So, Adc is fine.[/quote]

So, it seems either the hardware connection to the NTC is not correct, or the configuration of the SAADC to measure the NTC is incorrect.
Do you have the datasheet of the NTC sensor, so that you may verify that connections between your sensor and your nRF is correct?

[quote user="jpatel"]as I think at least Raw value needs to be changed based on temperature vary but not here. And I have a third party band and in that, I am trying to read the temperature.
In third party firmware, and in that temperature also vary based on heat. So, I think problem only with me.[/quote]

It could be that your connections to the sensor differ from what the manufacturer had intended.
To rule out the possibility that it is just the Steinhart forumla that is incorrectly implemented, could you write out the actual measured Voltage level for each of the channel, and see if that fits with the resistance curve in the datasheet?
I.e if you on channel 0 sample close to 3 V, then the thermistors resistance must be zero which corresponds to some reasonable temperature level. These are all random numbers, but could you see if you are able to read this out, to verify whether the results coming out of the SAADC are correct or not?
If we could verify that these results are reasonable, then we may move on to debugging the Steinhart forumla implementation.

Looking forward to resolving this issue together!

Best regards,
Karl

RE: Adc pin getting different results in during charging of board.

jaimin — Tue, 18 Aug 2020 04:51:07 GMT

Hi,

[quote userid="87869" url="~/f/nordic-q-a/64854/adc-pin-getting-different-results-in-during-charging-of-board/264891"]I would not think that you could do this. Are you sure this is the right way to go?
[/quote]

No, Karl, I have just searched in the browser and found a formula to read the NTC temperature using steinhart and I have applied that. Below link for formula.
https://github.com/panStamp/thermistor/blob/master/thermistor.cpp

[quote userid="87869" url="~/f/nordic-q-a/64854/adc-pin-getting-different-results-in-during-charging-of-board/264891"]You can uses the ADC_RESULT_IN_MILLI_VOLTS macro from the SAADC example to convert the raw SAADC output to millivolts.[/quote]

Ok but, I have check AIN1 and AIN2, raw AADC value not getting vary based on temperature.
I have tried to print Buff[0] and Buff[1] raw value of SAADC for AIN1 and AIN2 but that value not changed. I provided high or low heat using flashlight on the sensor to check the raw value of Ain pin but that not changed getting fixed value buff[0] = 700 and buff[1] = 350 around values.

So, I think ADC was not configured properly. To verify that, I have just change Ntc to battery voltage AIN pin and In that, I have to see Raw value changed based on increased or decreased battery voltage. So, Adc is fine.

as I think at least Raw value needs to be changed based on temperature vary but not here. And I have a third party band and in that, I am trying to read the temperature.
In third party firmware, and in that temperature also vary based on heat. So, I think problem only with me.

[quote userid="87869" url="~/f/nordic-q-a/64854/adc-pin-getting-different-results-in-during-charging-of-board/264891"]What custom module are you working with?
How is the USB 5V power routed compared to the battery power?[/quote]

No, Idea sir, We brought the band and In that load our custom firmware.

RE: Adc pin getting different results in during charging of board.

Karl Ylvisaker — Mon, 17 Aug 2020 13:24:26 GMT

Hello again,

[quote user="jpatel"]thanks for the reply[/quote]

No problem at all, I am happy to help!

[quote user="jpatel"]I am direct given the SAADC raw value to the Steinhart formula. [/quote]

I would not think that you could do this. Are you sure this is the right way to go?
The raw SAADC output will vary greatly based on the SAADC and channel configuration - I can not imagine that the formula accounts / scales for this.
Glancing over the Wikipedia page for the Steinhart-Hart equation ( if I am not mistaken ) it seems clear to me that you will need to provide the actual resistance value of the thermistors.
You can uses the ADC_RESULT_IN_MILLI_VOLTS macro from the SAADC example to convert the raw SAADC output to millivolts.

[quote user="jpatel"]And based on heat not changed value of temperature also.[/quote]

I am sorry, but I do not understand what you mean by this.

[quote user="jpatel"]If charging a band using USB and the same time if I read value then getting 0 value but after unplugged USB and read then different value of temperature.[/quote]

Is the only difference whether you connect a USB or not? This does indeed sound strange.
What custom module are you working with?
How is the USB 5V power routed compared to the battery power?

Best regards,
Karl

RE: Adc pin getting different results in during charging of board.

jaimin — Mon, 17 Aug 2020 11:26:40 GMT

Hi, Karl thanks for the reply,

I have a wrist band and that has an NTC sensor and NTC+ and NTC- are given in AIN1 and AIN2 (NRF52832), and charge band using USB(5V). I have attached the NTC screenshot here.
I have read the SAADC data and applied steinhart formula.
I have attached the file for code.
If charging a band using USB and the same time if I read value then getting 0 value but after unplugged USB and read then different value of temperature.
I am direct given the SAADC raw value to the Steinhart formula.
And based on heat not changed value of temperature also.
Please suggest I am in the right direction or not?

devzone.nordicsemi.com/.../11830.main.c

RE: Adc pin getting different results in during charging of board.

Karl Ylvisaker — Mon, 17 Aug 2020 10:49:45 GMT

Hello,

[quote user=""]I am working with custom board in that, trying to read NTC sensor value using 2 (NTC+ and NTC-) ADC pins.[/quote]

I understand that you are using a differential NTC sensor to measure temperature, so far so good.
Is it a particular NTC sensor you are working with, do you have its data sheet?

[quote user=""]After charging board unplugged and trying to read then, I am getting it's 37,36 value of temperature. But during charging It's I am getting 0 temperature value.[/quote]

Here things get a little more unclear. Could you please elaborate what you mean when you say "during charging" here, do you mean when the board is powered by USB as opposed to the coin cell battery, or what?
Which pins are you using for the measurements, and what is your SAADC and Channel's configuration? If you could provide a schematic or other document to indicate how you have connected your custom board with the NTC sensors, that would be helpful.
Please use the "Insert -> Code" option if you are going to share code.

[quote user=""]I have see during charging adc pin of (ntc+) = -2 around value and (Ntc-) = around 50 value get.
After charging unplugged and checked in that (ntc+) = 700 around and (ntc-) = 350 around value I am getting.
I have applied SAADC code from example/peripheral and configuration is internal reference voltage 0.6 and gain 1/6.
And Input charging is 5V. I don't know why I am getting 0 during Charging mode.
Can you please help?[/quote]

I am not sure I have understood the situation you refer to when you say that you are charging, but seeing as you mention 5 V input when charging I suspect that you refer to the board being powered by USB?

[quote user=""]Applied Steinhart formula to convert temperature.[/quote]

Are you first converting your samples to voltages, before inputting them to the Steinhart forumla? Or, are you providing the steinhart forumla with raw SAADC outputs?

Looking forward to resolve this issue together,

Best regards,
Karl