NTC measurement circuit bases in a Sigma-Delta Modulator or other suggestions?

Hello folks!

I need to design a conditioning circuit for a NTC with the attached datasheet:



The manufacturer recommend the next conditioning circuit based on a sigma-delta modulator:



It is important to comment that I need to convert the digital output of the sigma-delta modulator into analog values. It is a design requirement. Therefore a DSP in a FPGA o uC of the sigma-delta modulator ouptur is not allowed.

I tried to simulate the attached conditioning circuits with LTSpice, but I was not able to get the Spice model of the Sigma-Delta modulator part. So my questions are:

1) How to emulate in the output of the sigma-delta simulator with LTSpice if not any spice model of that part is available?
2) Is there any other ideas to conditioning the NTC temperature signal with the same accuracy than the sigm-delta conditioning circuit?

Thanks in advance to everyone.

Your motivation for performing the the analog-to-SD-to-analog conversion ist clear. Why not using the analog signal directly?

FvM said:

Your motivation for performing the the analog-to-SD-to-analog conversion ist clear. Why not using the analog signal directly?

Click to expand...

Because it is not recommended by the manufacturer because noisy environment where it is going to be placed the PCB board...Anyway, according to this special environment conditions, can you recommend me any signal conditioning circuit?

Thanks in advance.

The term "signal conditioning" seems misleading, the main circuit purpose is analog isolation.

The signal conditioning aspects are a voltage divider and a filter capacitor on the primary plus a second order low pass + level shift on the secondary side.

FvM said:

The term "signal conditioning" seems misleading, the main circuit purpose is analog isolation.

The signal conditioning aspects are a voltage divider and a filter capacitor on the primary plus a second order low pass + level shift on the secondary side.

Click to expand...

Ok. So the manufacturer solution is to get better measurements in harsh environments where high voltages (1.5kV) and high currents (300A) are running near of the NTC. However, do you think that if I choose the basic NTC transducer based on a wheatstone bridge and one OpAmp should it work fine too? Notice that my working environment is like I described before with high voltage and high currents. Should I take special consideration in my design like isolate the GND of the signal conditioning circuit? Thanks again