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Electronics => Beginners => Topic started by: Sikanda on September 13, 2023, 07:28:25 pm

Title: 4 to 20 mA ADC Interface
Post by: Sikanda on September 13, 2023, 07:28:25 pm

Hi,

On the Texas Instruments website I found a video about designing a multi-channel 4-20 mA analogue input module. The analogue module uses a Delta Sigma ADC - ADSS114S08. The ADC has 12 input channels. The author discusses three different ways of making the 4-20 mA interface to the ADC. Unipolar operation, extended unipolar operation using diodes to obtain a voltage offset and bipolar operation using dual supply. The author chooses the last one.

- Can you please look at the circuit below and tell me if I have done it as intended.
- Will I get offset voltages in the measurement due to the common reference point for all analogue inputs?

Video
https://www.ti.com/video/5461116970001 (https://www.ti.com/video/5461116970001)

Datasheet - ADSS114S08
https://www.ti.com/lit/ds/symlink/ads114s08.pdf (https://www.ti.com/lit/ds/symlink/ads114s08.pdf)

[attachimg=1]

Title: Re: 4 to 20 mA ADC Interface
Post by: langwadt on September 13, 2023, 07:34:43 pm

would make sense to move the TVS the other side of the PTC

Title: Re: 4 to 20 mA ADC Interface
Post by: Zero999 on September 13, 2023, 07:44:22 pm

Why use a non-standard value such as 4k? Why not 3k9 or 4k3? It won't make any difference. All those resistors do is limit the input current.

Title: Re: 4 to 20 mA ADC Interface
Post by: Sikanda on September 14, 2023, 05:18:45 pm

Thank you for the hints. Anything else? Is that the way to go?