I want to detect when the floating tag is grounded, thus allowing current to flow through R1 (54mA). I have found the following hall effect sensor here

It comes in 4 varities:

TMCS1100A1: 50 mV/A

TMCS1100A2: 100 mV/A

TMCS1100A3: 200 mV/A

TMCS1100A4: 400 mV/A

I am not sure how to interpret this sensitivity for each variation. Can someone help me to understand how those sensitivity values work? and what output voltage will I get for 53mA?

Also if the output is too low can someone help me in finding a new current sensor, either shunt or hall effect?


simulate this circuit – Schematic created using CircuitLab


1 Answer 1


The sensitivity spec is the output value per Amp of input. Eg. 50mV/A. If you pass 1A through the input, the device will output 50mV, 2A 100mV and so on. For 100mV/A - 1A in, 100mV out, 2A in, 200mV out.

Given the most sensitive device at 400mV/A, the output for an input of 54mA would be 54/1000 times 0.4V.

With hall effect current sensors, these are rather noisy, so for small signals these can get lost in the noise. The datasheet will specify this. At a rough guess (as I’ve not read the datasheet for your part) I’m thinking 54mA is getting a bit too low. It depends of if you want a reasonably accurate measurement or if you only want to roughly determine if there is some current flowing.

Product suggestions are off topic here, but if you tell us what your requirement are eg. Max current, resolution, accuracy, speed/frequency we can suggest circuit configurations that might suit.

  • \$\begingroup\$ Max current will be 54 to 60mA. Resolution I guess will be when 60mA is detected the output must around 4.9V and at 0 A the output will be around 0V, in between will follow a linear approximate. I'm not sure about the speed part can you provide more on this? \$\endgroup\$
    – JoeyB
    Commented Feb 16, 2022 at 5:09
  • 1
    \$\begingroup\$ @JoeyB. We have no idea of what you want to achieve, so you need to describe precisely what it is. Do you want to measure the current or simply activate an output if the current is 54mA or greater? If you want to measure the current then you might specify 0-60mA +/- 1mA and a resolution of 0.5mA. Output is 0-5V. Speed/frequency might be 100Hz or much more if the signal is detecting motor speed or such like. If you just want to detect the current, then maybe all you need is a relay? \$\endgroup\$
    – Kartman
    Commented Feb 16, 2022 at 5:36
  • \$\begingroup\$ I see. I do want to measure current, with the specs you mentioned in your comment " 0-60mA +/- 1mA and a resolution of 0.5mA. Output is 0-5V" \$\endgroup\$
    – JoeyB
    Commented Feb 16, 2022 at 21:59

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