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[SOLVED] bidirectional voltage measurement

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welove8051

welove8051

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hi, which is the efficient way to measure voltage in a bidirectional source. for example H bridge output at OP1 and OP2. a voltage divider and follower at either end measured with ADC or through a bridge rectifier at OP1 and OP2 then voltage divider, follower and ADC (to save one set of voltage divider and follower).

is there any other way to efficiently measure bidirectional voltage?

note: source V1 and V5 don't have common ground. is the above method right?

kindly comment

thanks
 

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"don't have common ground". Unlikely that they're fully floating against each other. But if so, a DC signal isolator is required. If an upper limit for the common voltage can be guaranteed an a certain leakage current is acceptable, the differential voltage divider solution is feasible. It will be usually combined with a differential amplifier.
 

Hi,

I agre with FvM.

Special care neets to be taken on selecting the voltage divider resistors.
The higher the common mode input voltage range, then higher the R_in/R_GND ratio. every deviation in this ratio (between both) generates a relatively large output signal error.
I recommend to use "true voltage dividers" (two calibrated resistors in one package) with low TC.

Klaus
 

how about using bridge rectifier at OP1 and OP2 before voltage divider?
 

Hi,

usually the bridge rectifier before voltage divider is more precise, but in detail it depends on circuit values.
(leakage currents, stray capacitance, load resistance...)

If there is no DC component you could use a transformer. If you are not interested in DC component, then a DC blocking capacitor in series to the primary widings may be useful.

Without knowing your circuit and what´s the target value of your voltage measurement is, it´s hard to give better assistance.
Target: V_avg, V_instantaneous, V_RMS? ... and what reaction time do you need?

BTW: There are ready to buy instrumentation amplifier ICs with input voltage range beyond supply rails.

--> show us your circuit.

Klaus
 

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