Measure a higher voltage than my O-scope can handle

[plukens]

This question seems so simple, I’m sorry to have to ask it….

I am driving a liquid droplet generator with a low frequency (100 Hz or less) square wave produced by my HP 214B pulse generator. I wish to monitor the signal with my oscilliscope at the same time. However, I cannot go above 30V peak because that is the input limit of my O-scope. I wish to go as high as 100 V, which is what my signal generator can produce. What simple device can I buy to reduce the voltage to my O-scope by a factor or 2, or perhaps 5 or even 10?

I have a x10 probe for the scope, but it has a sharp pointed tip. I need one with BNC connectors on both ends.

Something I can buy cheaply is the goal, perhaps on ebay. Making a voltage divider with resisters is my second choice.

 

[ronv]

Voltage divider should work fine.

 

[ChrisP58]

A 10X scope probe is basically a series connected 9 MegOhm resistor. Which, in combination with the 1 MegOhm input impedance of the scope, makes a 10:1 voltage divider.

In a 1X-10X probe, the switch just shorts out the 9M resistor.

 

[plukens]

Will this do the trick? Will this attenuate the voltage by a factor of 10?
Recall that I'm working at low frequencies. Less than 100 Hz.

**broken link removed**

Thanks.

 

[JimB]

Will this do the trick? No
Will this attenuate the voltage by a factor of 10? Yes

That attenuator is intended for use in 50 Ohm systems, and is only rated at 0.5 watt.
Your 100 volt square wave will make it dissipate about 100 watts. although I suspect that the generator will not be capable of producing anything like that power.

You need a x10 scope probe, some are available with BNC adaptors for the tips, you just have to look for them.

Other than that, you could make a simple voltage divider.
But be aware that you will need to frequency compensate it if you want to see square edges on your pulses.

JimB

 

[plukens]

A 10X scope probe is basically a series connected 9 MegOhm resistor. Which, in combination with the 1 MegOhm input impedance of the scope, makes a 10:1 voltage divider.

In a 1X-10X probe, the switch just shorts out the 9M resistor.

Thanks for the explanation. So what I'm seeking is a x10 probe with BNC connectors on both ends. I would think this to be common place, but I'm still looking.

 

[Nigel Goodwin]

Thanks for the explanation. So what I'm seeking is a x10 probe with BNC connectors on both ends. I would think this to be common place, but I'm still looking.

It's likely to be VERY rare, as almost no one would ever have a use for such a thing.

Use a standard x10 probe (which if you have a scoipe you really should have anyway) and clip that to a short wire from a BNC plug.

 

[ModemHead]

Thanks for the explanation. So what I'm seeking is a x10 probe with BNC connectors on both ends. I would think this to be common place, but I'm still looking.

Some scope probes, such as this one, come with a push-on BNC adapter for the probe tip.

 

[ronsimpson]

I made a BNC connector and soldered on to it some that my probe will clip to.
Maybe you don't have the clip on end just the sharp point......solder on a female socked that the sharp point will fit into.

 

[plukens]

That attenuator is intended for use in 50 Ohm systems, and is only rated at 0.5 watt.
Your 100 volt square wave will make it dissipate about 100 watts. although I suspect that the generator will not be capable of producing anything like that power.

You need a x10 scope probe, some are available with BNC adaptors for the tips, you just have to look for them.

Other than that, you could make a simple voltage divider.
But be aware that you will need to frequency compensate it if you want to see square edges on your pulses.

JimB

It's not clear to me if the resistance or the IMPEDANCE of the device shown above is 50 Ohms. Perhaps it is impedance matched for 50 Ohm networks but actually has a very high DC resistance? Isn't that how x10 probes work? They have a 10Megohm resistor and a capacitor?

Basically, I want a 10x probe with BNC connectors on both ends, as you suggest. This is a semi-permanent setup to monitor the signal driving the droplet generator at all times, not just a 1 time test.

Thanks for the help. If you know of an inexpensive device I can purchase with BNC on both ends, please do let me know.

 

[nsaspook]

In a pinch you can use a BNC tee with a test point wire for the scope probe connected to the third port. I've just soldered a short length of stiff wire to the female coax connector port socket in the past.

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