SensorsのトピックRe: RD9Z1-638-4Li-SW Current measurement

RD9Z1-638-4Li-SW Current measurement

bigoblue — Thu, 02 Jun 2016 02:14:59 GMT

Hi all

I’m working with the demo software provided by Freescale for RD9Z1-638-4Li-SW. I’m finding it when I reading the current measurement register (ACQ_CURR) there always something wrong (I think).Because when there is no load (only the board) I also see the current result is almost 200mA(the board consume is probably 20mA).

Is there some offset in the ACQ_CURR when I reading it. How can I get the really result or when the board is reset what is the result of the ACQ_CURR(it is 0xFFFFFF ?).
How Can I understanding the register ACQ_AHC? What is the unit of the register? How is the register increasing ? eg. When a current (150mA) runs one minute, I read the ACQ_AHC register increased 7690884.what is the meaning of the number 7690884?

Thanks for all answer!!!

Re: RD9Z1-638-4Li-SW Current measurement

bigoblue — Wed, 08 Jun 2016 08:26:32 GMT

the current flowing accross the shunt（100uΩ）
I want to measure the acctual current consumption of the board (no additional loads)
I used it.
when my Power GND connect to the CHASIS the current register was read as 0xFFFF94. when my Power GND connect to the BAT- the current register was read as 0xFFFF76(the result is always changing).The number of 0xFFFF94 is right，is it related to the hardware?
Thanks for the answer of Ah counter.

Re: RD9Z1-638-4Li-SW Current measurement

TomasVaverka — Wed, 08 Jun 2016 08:47:35 GMT

Hi,

I am just adding here Wolfgang’s answer to keep this thread consistent:

Depending on your setup you should see either ~0mA or ~35mA (typical current consumption of the board - no balancing, no additional loads).

Items to check:

in your setup is the current consumption of the board measured (flowing accross the shunt)
measure the acctual current consumption of the board
have you used the calibration values provided on the back of the shunt (sticker)

The Ah counter basically sums up all CSENSE measurements: AHC = SUM(CURR).

I expect in your setup the CSENSE is continuous running at 1KHz data rate. Which for 1 minute would be 60000 samples which are accumulated. So the average current Iaverage = SUM(CURR) / number_of_samples = 7690884/60000 = 128mA

Regards,

Tomas

Re: RD9Z1-638-4Li-SW Current measurement

Q_man — Fri, 10 Jun 2016 21:40:28 GMT

Hi,

You state that the 0xFFFF94 is right, why?

You measured:

0xFFFF94 (is -106 mA) in the Power Supply GND ------- BAT- terminal (Ishunt = Iload)
0xFFFF76 (is -136 mA) in the Power Suply GND ------> CHASSIS terminal (Ishunt = Iload - Isup)

With Iload = 0A, we can see that the Isup is about 30 mA (delta between both) and that we have a offset error of ~100mA. What values did you have on the Shunt sticker?

Did you measure Isup with an ext. Multimeter?

Re: RD9Z1-638-4Li-SW Current measurement

marinadioto — Tue, 18 Jul 2017 12:35:31 GMT

Hello!

I am using the MM912_637, but I am experiencing the same problem.. I always see an offset of around 150mA when comparing to the current value on the multimeter.

I am doing the calibration procedure and I am not being able to fix it. Does anyone could help me?

Maybe I am using the wrong configuration for the current ACD or doing the wrong procedure for the calibration.

Thank you,

Marina

Re: RD9Z1-638-4Li-SW Current measurement

Q_man — Thu, 20 Jul 2017 10:37:52 GMT

Hi Marina,

can you provide more details on your setup (schematics, where do you apply what, etc..)?

Re: RD9Z1-638-4Li-SW Current measurement

marinadioto — Mon, 24 Jul 2017 16:52:18 GMT

This is my setup:

Re: RD9Z1-638-4Li-SW Current measurement

Q_man — Fri, 18 Aug 2017 06:15:09 GMT

Marina, is the Chassis side floating? How does the current reading look like if you short Chassis to Battery Minus?

Re: RD9Z1-638-4Li-SW Current measurement

964839564 — Tue, 21 Apr 2020 10:42:54 GMT

HI ,

i use my board to measure voltage and current,but its value are increase all the time.Is there something wrong with my schematic or my program(KT9Z1_638_CAN_demo).

Thank you.

Best regards,

H YW