I've been following this discussion about diode power sensors.


I assume the diode sensors fail because of blown diodes form overload. Has any repaired the faulty sensors by replacing diodes?


Mike N2MS

On November 17, 2018 at 6:33 PM "Ed Breya via Groups.Io" <edbreya@...> wrote:

Hi Tobias, I looked at the OP again, and realized that you already knew about the "mount" resistor - I didn't notice that the first time. I grabbed that 8484A manual pdf that Orin linked - thanks Orin, I have lots of 8484As, and the manual somewhere, but can never seem to find it. Now I have a fresh copy.

Anyway, after refreshing my memory on these sensors, and looking also at the 8481A schematic, I'd recommend studying both types - the TC and diode models have a different arrangement for the auto-zeroing function. The circuit you posted puts the AZ feedback to the detector, as in the 8481A TC circuit, but that won't work right. With the TC type, it is a low impedance source, so the AZ current can go through, and offset the signal. With a diode detector, you should use a circuit like in the 8484A, which applies it to the ground-side JFET switch in the chopper. The diode detector is a high impedance source, so you don't want to put the AZ feedback current there.

Good luck,
Ed

On November 17, 2018 at 6:33 PM "Ed Breya via Groups.Io" <edbreya@...> wrote:

Hi Tobias, I looked at the OP again, and realized that you already knew about the "mount" resistor - I didn't notice that the first time. I grabbed that 8484A manual pdf that Orin linked - thanks Orin, I have lots of 8484As, and the manual somewhere, but can never seem to find it. Now I have a fresh copy.

Anyway, after refreshing my memory on these sensors, and looking also at the 8481A schematic, I'd recommend studying both types - the TC and diode models have a different arrangement for the auto-zeroing function. The circuit you posted puts the AZ feedback to the detector, as in the 8481A TC circuit, but that won't work right. With the TC type, it is a low impedance source, so the AZ current can go through, and offset the signal. With a diode detector, you should use a circuit like in the 8484A, which applies it to the ground-side JFET switch in the chopper. The diode detector is a high impedance source, so you don't want to put the AZ feedback current there.

Good luck,
Ed

The 12-pin circular connector used on the power sensors is an Amphenol.? The old part number was 91-T-3638.
Now, it's part of their "C 091 A/B/D" series circular connectors.? Several variations are listed in the Amphenol catalog:


Mouser has several slightly expensive options (a few of which appear in this link -- note that widening the Mouser search filter will supply more results):


It appears that an eBay seller is selling them at a lower price.? His text says they are the 12-pin versions, although his photo shows the 14-pin version.? It's hard to tell which of the two connectors he is selling.? However, it appears the two additional pins shouldn't matter since it's the female part of the connector -- you would leave those two extra pins unconnected.

Have you tried displaying your results on a Smith chart?

Check out Dr Joel Dunsmore’s book, “Microwave Component Measurements” for more than you ever wanted to know on the subject.?

On Nov 18, 2018, at 01:00, Gedas <w8bya@...> wrote:

Thanks for that. It does in fact say phase is measured +/- 180 degrees. Earlier I ran a quick test using the expanded phase format and I think it is in fact exactly what I want. Below is the same cable swept from 100 MHz to 300 MHz. The -90 degree and -180 degree points appear to be at the right frequencies. So if it will help others, un-wrapping phase or wrapping phase is very closely related to the expanded phase display format option of this ENA model. Too bad the users manual is useless in discussing these and so many other neat features.

<expand-phase-enabled.png>

Gedas, W8BYA

Gallery at 
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 11/17/2018 10:10 PM, nj902 wrote:

Gedas wrote: "Can someone point me to some reading material to help me understand how to measure phase ..."
------------------------------------------------------------------------------------------------------------------------------------------

Look for references on "unwrapped phase" measurement / display.

Like:

Staffan,
Have a look at python
I am from the generation that used to use FORTRAN IV and punchcards but you have to move up with times at some point.
Python has a few?idiosyncrasies that drive me mad but it's here to stay
I am using python as a goto choice for all my GPIB needs now.
Leo
On 18 Nov 2018, at 15:55, Staffan wrote:

Hello,

I can control the instrument so I guess termination is correct, but reading isn't working. I'd really like to do the low level byte by byte communication, but anyone knows hos to do this with 82357? Any hints would be highly appreciated!

Regards,
? Staffan

On Sun, 18 Nov 2018, 01:45 Gedas <w8bya@... wrote:

Can someone point me to some reading material to help me understand how to measure phase on my ENA?

You could save the data as a Touchstone file the import it into the software used for the VNWA.



and display as "c. phase" which is the phase unwrapped - I assume the c is for continuous.

Does your ENA support any sort of macro/programming? If so, you might be able to program something in there to unwrap phase.

There's no doubt the ENAs are pretty poor compared to the PNAs. The ENAs were developed in Japan and the PNAs in the USA. Support on the older ENAs on the Keysight forums is almost nonexistent.? The latest ENAs run the same firmware as the PNAs, so things are different.

I have the firmware of an ENA running on a PC (actually a virtual machine) as an emulator, but the ENA software is quite poor.

Dave, G8WRB.

Dear Gedas,

There is a way round this you might find useful- reference line extension function; I used this on an 8753B to take out the delay in a long optical delay line.

Essentially, you sweep over a frequency range that the DUT is phase linear over.?

Then adjust reference line extension until you get flat phase.?

Then read off the extension in ns.?

Then calculate the phase shift from frequency and delay.

I have n’t checked whether the same function is available for E series analysers; it would be a pity, if not.

Regards,

Alwyn

??

_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.

Tel.: +44 (0) 20 7376 4110


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.

_____________________________________________________

Have you tried displaying your results on a Smith chart?

Check out Dr Joel Dunsmore’s book, “Microwave Component Measurements” for more than you ever wanted to know on the subject.?

On Nov 18, 2018, at 01:00, Gedas <w8bya@...> wrote:

Thanks for that. It does in fact say phase is measured +/- 180 degrees. Earlier I ran a quick test using the expanded phase format and I think it is in fact exactly what I want. Below is the same cable swept from 100 MHz to 300 MHz. The -90 degree and -180 degree points appear to be at the right frequencies. So if it will help others, un-wrapping phase or wrapping phase is very closely related to the expanded phase display format option of this ENA model. Too bad the users manual is useless in discussing these and so many other neat features.

<expand-phase-enabled.png>

Gedas, W8BYA

Gallery at 
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 11/17/2018 10:10 PM, nj902 wrote:

Gedas wrote: "Can someone point me to some reading material to help me understand how to measure phase ..."
------------------------------------------------------------------------------------------------------------------------------------------

Look for references on "unwrapped phase" measurement / display.

Like:

Hi Guys,

sorry for my late reply.

Today I was able to make some further progress. Robert was right in his post (/g/HP-Agilent-Keysight-equipment/message/92641) - the autozero problem I encountered was indeed related to the position where I connected the autozero signal. In principle, I have now the same schemativ as the 8484A diode power sensor.
After moving the autozero signal, I still had the problem that the autozero did not work properly, so I further analyzed the circuit of the 8484A and realised that it has less gain than my circuit, so I changed the base resistor of Q1 () to 1k Ohms and the autozero problem was fixed - pressing the autozero button perfectly allows the meter to zero the sensor. However, with this modification, my sensor had a different gain, and therefore the readings on the meter had an offset. I was able to re-adjust the gain with the trim pot and when I put a 10dB attenuator at the sensor input, I was able to have the same readings on the meter as on the signal generator I used to test the sensor. However, as I said, it is not terribly accurate, at very low power levels, it was around -1dB off, and at high power levels, it seems like the diode transitions from square law region to linear region and therefore the readings were also off a bit. But this is no big deal; one can simply add attenuators in front of the sensor such that it is ensured the diode is in its square law region.

Thanks at Orin for the 8484A sensor schematic. I have never found it, even though I was of course looking for it.

Joarez (/g/HP-Agilent-Keysight-equipment/message/92646) says that the capacitors need to be there to prevent the circuit from generating switching abberations. This is probably true because the 8484A manual tells that the capacitors were factory selected individually for each sensor, so they are probably related somehow to the JFET switches. In my sensor, I currently don't have these capacitors, and this is probably another reason why the readings are not 100% accurate. It could also be related to the JFETs I use - I chose the first ones I could get, but somewhere in my junk boxes I should have a pile of 2N4856, which are probably better. However, I would prefer SMD devices since I will make a PCB in SMD design. I got a bunch of MMBFJ310, but I have not enough of them to make a lot of experiments :-/


Thanks also to rmc321 and Rainer for the link to the connectors. I was once told that HP used their own connectors, so I didn't even try too hard to find the connectors, but very good you found them! I could have saved my valuable power sensor cable if I had known it earlier :-)

I think I am soon going to make another dead bug prototype and in parallel design a PCB and probably my own housing. I will share the design files as soon as I am ready.

Tobias HB9FSX

The 12-pin circular connector used on the power sensors is an Amphenol.? The old part number was 91-T-3638.
Now, it's part of their "C 091 A/B/D" series circular connectors.? Several variations are listed in the Amphenol catalog:


Mouser has several slightly expensive options (a few of which appear in this link -- note that widening the Mouser search filter will supply more results):


It appears that an eBay seller is selling them at a lower price.? His text says they are the 12-pin versions, although his photo shows the 14-pin version.? It's hard to tell which of the two connectors he is selling.? However, it appears the two additional pins shouldn't matter since it's the female part of the connector -- you would leave those two extra pins unconnected.

Hi Staffan

Yes, you need to meter to be in addressable mode (or as you say, "normal").
If you use the interactive IO, you would use the "Send and Read"..? Type the command to fetch the reading in the text box, and use the "Send and Read" button, which will set the computer as the talker, send the command, and then it sets it up so the meter is the talker.? You should see the results show up in the history below.? It puts the actual results there, with no additional formatting so you can see exactly what it sends back.? Of course you can also do it individually using the separate "Send Command" and "Read Response" as well. The "Send and Read" just combines the two actions.
What language do you plan to use for your program?

Daun

On 11/17/2018 4:52 PM, Staffan wrote:

Hello,

Just got hold of an old HP436A power meter and would like to do some automated measurements. Controlling the instrument is simple using the 82357B USB-GPIB module (I can set range etc), but reading data? As a first step I'd like to test using Agilent Interactive IO from Connection Expert. If that works, I'm fairly sure I can get it working in a program also.?
The 436 is set to NORMAL, i.e., not TALK ONLY. It does have the HP-IB option 022 installed. My guess is that I need to address the instrument to Talk in some other way than the "Read Response" used in Interactive IO.

Anyone with experience of this?

Regards,
? Staffan

?

--
Daun E. Yeagley II, N8ASB

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