TMUX1208: TMUX1208 with 4-20mA loop signals

Marc MORAND

Part Number: TMUX1208
Other Parts Discussed in Thread: RCV420, TMUX7208, INA180, TLV9001

Tool/software:

Dear TI Support,

I need to interface Sensors in an industrial gloove box, O2 Sensor with passive with 2 wires 4-20mA output and H2O Sensor active with 3 wires 4-20mA.

These sensors are supplied with external +24V.

I would like to know if i could use your TMUX1208 for multiplexing 4-20mA input signals to send to a RCV420 4-20mA loop receiver?

The RCV420 is supplied with +/-15V .

Thanks for your help,

Best Regards,

Marc MORAND

2 months ago

0 Clemens Ladisch 2 months ago

Guru 316690 points

What are the TMUX's supply voltages? What are the signal voltages?

0 Kameron Hill 2 months ago in reply to Clemens Ladisch

TI__Mastermind 24440 points

Hi Marc

Could you also show us a schematic of your design idea?

Regards,

Kameron

0 Marc MORAND 2 months ago in reply to Kameron Hill

Prodigy 20 points

TI_Support_250619.pdf

Dear Support,

Please see "TI_Support_250619.pdf" file.

To my mind, it seems that TMUX1208 supply voltage is not compatible with 4-20mA signal voltage from my sensor?

nevertheless is it possible to connect the 4-20mA signal of my sensor directly to the input of the RCV420?

Thanks for your help.

Best Regards,

Marc,

0 Marc MORAND 2 months ago in reply to Clemens Ladisch

Prodigy 20 points

Hi Clemens,

The TMUX supply voltage is +5V and my sensor supply voltage is +24V.

Is it the same voltage on the 4-20mA signal wire? if Yes it doesn't work!!

But just a last question, is it possible to connect directly 4-20mA sensor signal to the input of a RCV420 powered with +/-15V?

Thanks for your help,

Regards,

Marc,

0 Clemens Ladisch 2 months ago in reply to Marc MORAND

Guru 316690 points

A current of 20 mA flowing through 150 Ω results in a voltage of 3 V, which would be OK. But the voltage at an inactive switch input, when no current flows, would be too high.

You can use the TMUX7208 with ±15 V supplies instead.

The RCV420 accepts ±40 V input voltages. But why are you using it? A resistor and a plain current-sense amplifier like the INA180 would be cheaper and more accurate.

0 Marc MORAND 2 months ago in reply to Clemens Ladisch

Prodigy 20 points

Thanks for your prompt reply

What is the best value for RSense with INA180 device? 250 ohms ( to obtain 5V with 20mA).

I did not know this type of device. is it really more accurate than RCV420?

Thanks for your help

Regards,

Marc,

0 Clemens Ladisch 2 months ago in reply to Marc MORAND

Guru 316690 points

The INA180 amplifies by at least 20, so you would need 12.5 Ω.

If the measuring resistor is connected to GND, you could simply use a plain opamp (e.g., TLV9001) as a buffer.

If the signal goes to an ADC with a 5 V supply, you might want a little headroom, so use something like 12.1 Ω or 237 Ω.

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TMUX1208: TMUX1208 with 4-20mA loop signals