Hi Joaquim,

There is no spice model available for the ADG1409.  The spice models we have available are at this site http://www.analog.com/en/tools-software-simulation-models/resources/index.html

Rgds,

Theresa.

Parents
• Hi Theresa,

1. You say that results are good for the V and PT100 measurements but not linear for the 4-20mA.  Can you give details.

- My results are based in Spice simulations. For PT100 and V, I'm measuring voltage and I think the Ron of ADG4612 don't affect to the signal conditioning. The voltage is lineal for a lineal variation at the input. The gain of AD627 is 5. For example for V input and for 5V the AD627 input(pins 2 and 3)/output(pin 6) is 0.2244508/1.1222541V and for 10V the output is 0.4489016/2.2445081V. Is exactly the half and is lineal. Note that only R1 and R2 are connected.

- For 4-20mA signal conditioning is not lineal for a lineal input. For 4mA the AD627 input (now only R3 is activated) is 0.0404V and for 8mA the AD627 input is 0.0801V, when it would be 0.0808V (or very close). I think this is because Ron varies with the voltage across it, and it's caused for the variation of mA input. This variation is added to the voltage measure. I think is not problem for the AD627. The problem is that the mA input are directly connected to the swicth. What do you think?

2. Have you looked at results at temperature?

- Not still. I'm doing a prototype of the signal conditioning for a real test.

3. For 4-20mA it appears you have 10ohm gain resistor switched in, gain of 20k?  Can you clarify this?  What tolerance R's are you using?

- My gain is 5 because the pins 1 and 8 of the AD627 are unconnected. R3 = 10 Ohms is the mA shunt. For translating mA to voltage. I'm using a 1% tolerance resistors.

My critical point is how do a 4-20mA lineal signal conditioning with switch and mux.

Thank you very much.

• Hi Theresa,

1. You say that results are good for the V and PT100 measurements but not linear for the 4-20mA.  Can you give details.

- My results are based in Spice simulations. For PT100 and V, I'm measuring voltage and I think the Ron of ADG4612 don't affect to the signal conditioning. The voltage is lineal for a lineal variation at the input. The gain of AD627 is 5. For example for V input and for 5V the AD627 input(pins 2 and 3)/output(pin 6) is 0.2244508/1.1222541V and for 10V the output is 0.4489016/2.2445081V. Is exactly the half and is lineal. Note that only R1 and R2 are connected.

- For 4-20mA signal conditioning is not lineal for a lineal input. For 4mA the AD627 input (now only R3 is activated) is 0.0404V and for 8mA the AD627 input is 0.0801V, when it would be 0.0808V (or very close). I think this is because Ron varies with the voltage across it, and it's caused for the variation of mA input. This variation is added to the voltage measure. I think is not problem for the AD627. The problem is that the mA input are directly connected to the swicth. What do you think?

2. Have you looked at results at temperature?

- Not still. I'm doing a prototype of the signal conditioning for a real test.

3. For 4-20mA it appears you have 10ohm gain resistor switched in, gain of 20k?  Can you clarify this?  What tolerance R's are you using?

- My gain is 5 because the pins 1 and 8 of the AD627 are unconnected. R3 = 10 Ohms is the mA shunt. For translating mA to voltage. I'm using a 1% tolerance resistors.

My critical point is how do a 4-20mA lineal signal conditioning with switch and mux.

Thank you very much.

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