I'm interested in the voltage @ the supply end.[/QUOTE]First thing you have to decide is: What voltage do you need to know?
* the voltage at the DUT, or
* the voltage at the supply
(Often with ATE you need to know the voltage at the DUT, but in your configuration it is the voltage at the supply.)
It depends. The initial post is suggesting common mode errors due to ground voltage drops. If they are relevant, you'll surely need differential amplifiers. But up to now, nothing has been said about expected common mode errors and accuracy requirements. If the requirements are beyond a semiquantitative 10 bit measurement, differential amplifiers should be in fact considered.Using an op amp to measure the supply voltage is purely academic and has no benefit.
Use 2 resistors.
It depends. The initial post is suggesting common mode errors due to ground voltage drops. If they are relevant, you'll surely need differential amplifiers. But up to now, nothing has been said about expected common mode errors and accuracy requirements. If the requirements are beyond a semiquantitative 10 bit measurement, differential amplifiers should be in fact considered.
This is true only when the op amp don't introduce any error.It depends. The initial post is suggesting common mode errors due to ground voltage drops. If they are relevant, you'll surely need differential amplifiers. But up to now, nothing has been said about expected common mode errors and accuracy requirements. If the requirements are beyond a semiquantitative 10 bit measurement, differential amplifiers should be in fact considered.
I could agree if I knew more about the ADC parameters.For voltage measurement i'd use two resistors and a capacitor at each input
But in detail one need "ADC input voltage range", max gnd bouce range, power supply voltage range(to be measured)...I have differential ADCs in the controller.
Klaus and FvM, This could be one of those rare cases that both sides a right.Hi,
Yes, given is just
But in detail one need "ADC input voltage range", max gnd bouce range, power supply voltage range(to be measured)...
And so on...
Klaus
For ground ref ADC you can use resistors dividers for measuring voltages. Use the circuit on post #3 to measure the currents.The reason I was using the op-amp is that it seems more flexible for signal conditioning.
What if the ADC was ground referenced?
I agree with this approach. Even if the ADC has differential imputs, it may still require an amplifier to achieve the common mode voltage specification. Required ADC source impedance is another point that can suggest an amplifier.The reason I was using the op-amp is that it seems more flexible for signal conditioning.
What if the ADC was ground referenced?
What if the ADC was ground referenced?
DO NOT start design until you define, Resolution, accuracy V range, I range for each input in a short spec and then Environmental stress for inputs.
Ensure all Vref measurements use best Star ground otherwise ADC will have missing codes or monoticity errors from ground shift.
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