I'd like to clarify your requirements:
Vout = Vin - 1 V
Is the DC range 0 - 2 V for the Vin or Vout?
Does the Vout need to go negative voltage?
What is the output current requirement?

Best,
Eric

Best,

Eric Preiss | Applications and Validation Engineer | Linear and Low Dropout Regulators | Texas Instruments

It sounds like a difference amplifier would work for your application my only concern is that the input impedance of the difference amplifier may effect the performance of the impedance transducer. I'm not familiar with an impedance transducer, can you provide a datasheet of the impedance transducer?

Why do you need to subtract only 1V off of the input?

An instrumentation amplifier such as the INA116 can provide a very accurate design for pH sensors. Have you considered this approach?

Hi Tim,
1) Our new measuring pH-transducers give 0-20mA. The subsequent electronic system works with voltage. The current is transformed via 100Ohm precision resistance so we get 0-2V. *)
2) The primary voltage after the old impedance-transducers stayed within +1V. And again all subsequent electronic systems and software work within the limit. The conversion is time-consuming and so we look for a completed answer.
3) We frame as a possible solution the described DC voltage reducer:
- voltage rail 24V=
- Vout = Vin-1V
- Vin DC range = 0-2V
- Vout = max. +1V
- Current is very less
The convenience is we only have to put the voltage reducer between Vout and the follow present subsequent electronic systems.
*) we can use other resistance e.g. 500 Ohm so we get 10V and accordingly we wish to reduce
Best, Erwin

How about the circuit below? It converts 0-2V into 0-1V and has an input impedance of 1.5MOhms. It was difficult to understand from your requirement but it seems like the circuit goals are to attenuate a 2V signal into a 1V signal, not necessarily just to subtract 1V from the input.

In my reply to Timothy Claycomb I wrote Vout = max. +1V. Sorry I forgot the minus-sign. Vout must be plus/minus 1V.

The measurement range of an pH-electrode is plus/minus 0,5V.

So the voltage is not to be sufficient to reduce from 2 to 1V but if a modified above circuit will convert it to minus would be nice.

For example please see the diagram

Index A stands for Ausgang = Out and E for Elektrode = Electrode

In the example 0-20 mA gives via 12,4 Ohm an output 0-248mV. What we need in that case is an output plus/minus 470mV. So the 0-248mV output has to convert to minus/plus.

But for generally purpose we prefer an output extended range plus/minus 1V for an input 0 to 2V.

For an output voltage of +/-1V you will need to use dual supplies, for example +/-15V. You mentioned you have a +24V supply available but do you also have a negative supply rail available? If so, what is the negative supply voltage you have available?