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I want to measure and log a relatively high variable voltage signal, with minimum impact on the original signal.

Normally the signal should average 130volts and vary by +/- 20volts at 10Hz. However under different circumstances all these parameters are likely to change.

I would like to log these changes, but the problem is my data logger can only support volatages up to 60v DC or 42v AC.

I have considered using a small transformer, but fear that the relatively slow frequency may not induce a representative current in the secondary coil. And/or the variable frequency may result in back emf, corrupting the original signal.

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  • $\begingroup$ Resistive divider. $\endgroup$ – Marcus Müller Dec 30 '17 at 13:09
  • $\begingroup$ Thanks @MarcusMüller that would certainly be very simple. Should I concerned about the sizing of the resistors? I guess the bigger the better. $\endgroup$ – Colin Dickie Dec 30 '17 at 13:49
  • $\begingroup$ depends on the source impedance of the voltage source $\endgroup$ – Marcus Müller Dec 30 '17 at 14:05
  • $\begingroup$ What you need is known as signal conditioning. You need to scale your input signal to something that your data acquisition hardware can handle. You can buy or build hardware to do what you need. If you find you must build your own (or you want to build it for the fun/learning effect) the you might visit the electronics stack exchange. $\endgroup$ – JRE Dec 30 '17 at 16:21
  • $\begingroup$ @MarcusMüller, i would call that a "resistive voltage divider". if Colin's data logger is okay with voltage difference, that's all that he needs. but sometimes these are single-ended, uni-polar devices that measure a voltage against their own ground. and sometimes the high voltage (difference) you're trying to measure is floating around somewhere else. this is sometimes why isolation transformers are useful. $\endgroup$ – robert bristow-johnson Dec 30 '17 at 20:40

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