Author Topic: How to interpret HP 1141A max voltage specs?  (Read 708 times)

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Offline _Wim_

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How to interpret HP 1141A max voltage specs?
« on: October 07, 2018, 08:35:00 am »
Hi, I acquired and 1141A (and 1142A) recently, but the probe came without the attenuators or AC-coupler. Attached is a couple of screenshots of the main specifications.

Maximum Input Voltage:
Am I correct saying the probe without attenuator withstands (iow before damage) max 200Vdc+ac to 200kHz? This max voltage is referenced to ground, and is for both the + and – input (so it can be common or differential). Above 200kHz this rating drops to max 5Vp at 7Mhz. If this is correct, the risk of actually damaging the probe seems quite ok, even without attenuator.

Differential Input Range:
Max measured differential signal is 300mVpeak for the complete frequency range. Above that the signal clips or distorts? Why is there the additional note 1 “For maximum signal fidelity above 100 MHz, limit the probe input (without attenuators to 300 mV)”? Does this mean that even with the attenuators the differential signal must be limited to 300mV peak to avoid distortion? The specs for 10x and 100x above 30Hz contain a typo, right? (mV must be V)

Common-mode Operating Range:
What is exactly meant with the common mode operation range of 0.5V between 30Hz and 200Mhz. Does this mean the CMRR will be lower than what is shown in figure 3-1 if the common mode signal goes above 0.5V? But at 200Mhz the CMRR is only 1/10, so a common mode signal of 0.5V will already give 50mV of noise, so surely not very useable any longer here? Or is there a risk of damage is the common mode signal goes above 0.5V (that would then be contradictory to figure 3-2). This spec I find the most confusing.


This is probably obvious for many, but it is confusing me and would like to prevent damage to this probe.
 

Online Kleinstein

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Re: How to interpret HP 1141A max voltage specs?
« Reply #1 on: October 07, 2018, 10:02:53 am »
The 200 V limit seems to apply to the probe without attenuator. But be aware that it is AC peak. So more like 140 V RMS if a pure sine.

The  < 300 mV note for > 100 MHz likely applies to the common mode signal, because the CMRR is not that good anymore at high frequency.

I agree with the typo for the 3 mV/30 mV limit for the case with attenuator, but without the attenuator it does not really matter.

The common mode operating range applies to getting more errors when leaving this range, not damage.
 

Offline _Wim_

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Re: How to interpret HP 1141A max voltage specs?
« Reply #2 on: October 07, 2018, 10:10:02 am »
The 200 V limit seems to apply to the probe without attenuator. But be aware that it is AC peak. So more like 140 V RMS if a pure sine.

The  < 300 mV note for > 100 MHz likely applies to the common mode signal, because the CMRR is not that good anymore at high frequency.

I agree with the typo for the 3 mV/30 mV limit for the case with attenuator, but without the attenuator it does not really matter.

The common mode operating range applies to getting more errors when leaving this range, not damage.

Thanks for your reply. Yes, I know it is AC peak, but still, 200V is quite ok. My main goal for this probe is powerrail noise measurement, so 200V peak is quite enough. I have no intention to probe mains voltage or something like that...
 


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