Readout pin on oscilloscope probes

[Philipp Klaus Krause]

Where can I find information about the readout pin present on some
oscilloscope probes? Googling just turns up lots of pages of people
selling such probes, but no protocol documentation, etc.

Philipp

 

[PeterD]

Where can I find information about the readout pin present on some
oscilloscope probes? Googling just turns up lots of pages of people
selling such probes, but no protocol documentation, etc.

Philipp

You talking about that small pin that is part of the BNC connector? If
so, it's function is simple, it connects to ground when in the 10X
mode, IIRC.

 

[Philipp Klaus Krause]

You talking about that small pin that is part of the BNC connector?
Yes.

If
so, it's function is simple, it connects to ground when in the 10X
mode, IIRC.

Thanks (I expected it to be more complicated though).

Does that mean it's just disconnected in X1 mode? What about X100?

Philipp

 

[Jim Yanik]

Thanks (I expected it to be more complicated though).

Does that mean it's just disconnected in X1 mode? What about X100?

Philipp

try www.tek.com.

 

[Atsunori Tamagawa]

Thanks (I expected it to be more complicated though).

Many of these probes have a resistor between the read-out pin and its
ground. And in case of some Tektronix scopes, they use this resistor
and scope's internal resistor to form a voltage divider to devide some
know internal reference voltage. They look at the divided voltage to
determine the type of probe connected.

Since I had nothing better to do this afternoon at work, I decided to
measure this resistance for probes around me. So the following table
was made.

Probe Series R Type Readout R
----------- -------- ------ ----------------------
TEK P6053 9M x10 INFINITY
TEK P6062B 360/9M x1/x10 INFITITY/12K
TEK P6106 9M x10 11K
TEK P6130 9M x10 11K
TEK P6131 9M x10 11K
TEK P6137 9M x10 11K
TEK P6138A 9M x10 11K
TEK P6139A 9M x10 11K
HP 10073A 900K x10 11K
HP 10441A 900K x10 obviously zero(3-1ohm)
LeCroy PP062 500 x1(?) 11K

This is why when I connect LeCroy PP062 to Tek scope, it thinks it's
a x10 probe, but actually I get ten times bigger waveform.

Then I became even more curious. So I used bunch of 1K ohm and other
resistors to "test" how Tek scopes judge probe types based on this
resistance. To my surprise, somewhat modern TDS684B distinguished 7
different probe types including x1 as default. Following table is the
result.

Readout R TDS684B 2465DMS
--------- ------- -------
11k x10 x10
10k x10 x10
9k x10 x10
8k x10 x100
7k x100 x100
6k x100 x100
5k x100 x1000
4k error x1000
3k x2 x1000
2k x5 x1000
1k x200 x1000
510 x1000 ID mark

I've never seen x2, x5, x200 or x1000 probes myself, as well as I'm not
sure if my afternoon was well spent today.

Atsunori

 

[PeterD]

Many of these probes have a resistor between the read-out pin and its
ground. And in case of some Tektronix scopes, they use this resistor
and scope's internal resistor to form a voltage divider to devide some
know internal reference voltage. They look at the divided voltage to
determine the type of probe connected.

Since I had nothing better to do this afternoon at work, I decided to
measure this resistance for probes around me. So the following table
was made.

Probe Series R Type Readout R
----------- -------- ------ ----------------------
TEK P6053 9M x10 INFINITY
TEK P6062B 360/9M x1/x10 INFITITY/12K
TEK P6106 9M x10 11K
TEK P6130 9M x10 11K
TEK P6131 9M x10 11K
TEK P6137 9M x10 11K
TEK P6138A 9M x10 11K
TEK P6139A 9M x10 11K
HP 10073A 900K x10 11K
HP 10441A 900K x10 obviously zero(3-1ohm)
LeCroy PP062 500 x1(?) 11K

This is why when I connect LeCroy PP062 to Tek scope, it thinks it's
a x10 probe, but actually I get ten times bigger waveform.

Then I became even more curious. So I used bunch of 1K ohm and other
resistors to "test" how Tek scopes judge probe types based on this
resistance. To my surprise, somewhat modern TDS684B distinguished 7
different probe types including x1 as default. Following table is the
result.

Readout R TDS684B 2465DMS
--------- ------- -------
11k x10 x10
10k x10 x10
9k x10 x10
8k x10 x100
7k x100 x100
6k x100 x100
5k x100 x1000
4k error x1000
3k x2 x1000
2k x5 x1000
1k x200 x1000
510 x1000 ID mark

I've never seen x2, x5, x200 or x1000 probes myself, as well as I'm not
sure if my afternoon was well spent today.

Atsunori

That afternoon was very well spent! I learned that something other
than X10 was supported, which I didn't realize, and those numbers are
very interesting!

 

[John Devereux]

Many of these probes have a resistor between the read-out pin and its
ground. And in case of some Tektronix scopes, they use this resistor
and scope's internal resistor to form a voltage divider to devide some
know internal reference voltage. They look at the divided voltage to
determine the type of probe connected.

Since I had nothing better to do this afternoon at work, I decided to
measure this resistance for probes around me. So the following table
was made.

[...]

I've never seen x2, x5, x200 or x1000 probes myself, as well as I'm not
sure if my afternoon was well spent today.

Atsunori

That afternoon was very well spent! I learned that something other
than X10 was supported, which I didn't realize, and those numbers are
very interesting!

Also see e.g.

<http://www2.tek.com/cmswpt/faqdetails.lotr?ct=FAQ&cs=faq&ci=4290&lc=EN>

 

[Philipp Klaus Krause]

I've never seen x2, x5, x200 or x1000 probes myself, as well as I'm not
sure if my afternoon was well spent today.

Thanks a lot for what you found out. I'll try to do the same for another
scope and report what I find here.

Does anyone know where one can get BNC connectors with the outer metal
ring that connects to the probe pin? Maybe it's easier to just use a
normal connector and add the ring myself though.

Philipp

 

[Philipp Klaus Krause]

Also see e.g.

<http://www2.tek.com/cmswpt/faqdetails.lotr?ct=FAQ&cs=faq&ci=4290&lc=EN>

There's lots of probe interfaces mentioned there. However AFAIK only
Plain BNC and what they call "TekProbe-BNC Level 1" are some kind of
industry standard. The rest seem to be Tektronix proprietary.

Philipp

 

[Philipp Klaus Krause]

Many of these probes have a resistor between the read-out pin and its
ground. And in case of some Tektronix scopes, they use this resistor
and scope's internal resistor to form a voltage divider to devide some
know internal reference voltage. They look at the divided voltage to
determine the type of probe connected.

Since I had nothing better to do this afternoon at work, I decided to
measure this resistance for probes around me. So the following table
was made.

Probe Series R Type Readout R
----------- -------- ------ ----------------------
TEK P6053 9M x10 INFINITY
TEK P6062B 360/9M x1/x10 INFITITY/12K
TEK P6106 9M x10 11K
TEK P6130 9M x10 11K
TEK P6131 9M x10 11K
TEK P6137 9M x10 11K
TEK P6138A 9M x10 11K
TEK P6139A 9M x10 11K
HP 10073A 900K x10 11K
HP 10441A 900K x10 obviously zero(3-1ohm)
LeCroy PP062 500 x1(?) 11K

This is why when I connect LeCroy PP062 to Tek scope, it thinks it's
a x10 probe, but actually I get ten times bigger waveform.

Then I became even more curious. So I used bunch of 1K ohm and other
resistors to "test" how Tek scopes judge probe types based on this
resistance. To my surprise, somewhat modern TDS684B distinguished 7
different probe types including x1 as default. Following table is the
result.

Readout R TDS684B 2465DMS
--------- ------- -------
11k x10 x10
10k x10 x10
9k x10 x10
8k x10 x100
7k x100 x100
6k x100 x100
5k x100 x1000
4k error x1000
3k x2 x1000
2k x5 x1000
1k x200 x1000
510 x1000 ID mark

I've never seen x2, x5, x200 or x1000 probes myself, as well as I'm not
sure if my afternoon was well spent today.

Thanks for your inspiration on how to spend a nice afternoon!
Here's the results (not that much, the equipment is old, most of the
stuff doesn't have readout pins):

Probe Type Readout R
---------- ---- ---------
TEK P6111B x10 11k4
TEK P6114B x10 11k1

Readout R TDS360
--------- ------
20k x1
16k x1
15k x10
13k x10
12k x10
11k x10
8k2 x10
7k5 x10
6k8 x100
5k6 x100
4k7 x100
3k6 x1
3k x1
2k7 x10
2k4 x2
2K2 x2
2K x5
1k8 x5
1k6 x20
1k5 x10
1k3 x20
1k2 x50
1k1 x50
1k x200
820 x200
750 x500
680 x500
620 x500
560 x1000
470 x1000
360 x1000
300 x1
100 x1
10 x1

Looks like they started using whatever resistor they had (2k7, 1k5) to
mark x10 probes and later came up with a more generic scheme, but had to
leave some intermediate values at x10 for backwards compability.

Philipp

 

[Philipp Klaus Krause]

Many of these probes have a resistor between the read-out pin and its
ground. And in case of some Tektronix scopes, [...]

Is this the same as Agilent Autoprobe?

Philipp