oscilloscope probe question

[aliyesami]

my TEK2467B scope says 1Mohm 15pf on its channel inputs but the manual is recommending P6137 probe which is 10Mohm 10.8pf probe so how does it work ?
Iam not understanding the probes correctly I guess

thanks

 

[FvM]

P6137 is covering an oscilloscope input capcitance range of 12 to 18 pF (by an adjustment screw), so it's just fine. Don't confuse probe input and channel input capcitance (although they are same order of magnitude)

 

[aliyesami]

what about the resistance ? I am not understanding the relation between the resistance and capacitance value written on the scope channel to the probe.
let me ask this question in another way. I have another scope TDS380 for which i have no idea which probe to use , how will i go about finding one? i mean on which criteria?

thanks for your patience i am totally new to scopes and learning.

 

[Venkadesh_M]

in low frequency The resistance of the probe shdnt load your source and the capacitance shdnt deform your waveform for it you can choose a probe(usually everything works)...

for very high frequency the impedance shdnt produce any reflection of wave so it shd matched(both are nearly equal) with your circuit output impedance....

 

[FvM]

I thought you are worrying about probe matching.

For probe selection in generally, you usually think about probe impedance, mostly input capcitance, voltage range and bandwitdth. A passive 10:1 probe is appropriate for most measurements. You need the attenuation to achive an acceptable low input capacitance and also voltage range up to several 100 V. For sensitive measurements, a 1:1 probe may be preferred, but unfortunately it exposes a high input capacitance (oscilloscope + cable capacitance) usually > 100 pF. That's only accepatble for a few low speed measurement problems.

 

[aliyesami]

so that means i can use P6139A with my TEK 2467B scope . but why am i getting a jagged sine wave if i connect the probe to the on board test point that generates a 4KHz square wave even though i played with the attunator adjustor screw ?
what am i doing wrong here?

 

[Venkadesh_M]

continuity test will help you to check probe and verify that your signal pin is connected and proper channel selected and other all settings remains default with DC coupling.....

 

[FvM]

The probe adjustment should be made with the oscilloscope test signal. The adjustment is for over/undershoot of a square wave. A wrong probe adjustment doesn't fake a sine wave. You possibly get ringing edges when probing fast signals (in a high MHz range) with incorrect probe ground connection.