HP 437B Power Meter with HP 8481A and HP 8484A Power Sensors
Вставка
- Опубліковано 18 кві 2016
- I just recently purcahsed a new power sensor off eBay, a HP 8484A -70dBm to -20dBm for my HP 437B Power Meter. LEt's take a quick look at setting it up and reading a power value.
- Наука та технологія
First time getting into using Power Sensors with understanding frequency profiles. Good starting point demonstration.
Thanks - Appreciate the feedback.
thank u for video sir ,pls suggest for using power meter using for 2ghz bcoz the set value was set value for 50 mhz during calibration
There are two ways to set the calibration factor. You can just set it directly for the frequency that you want to measure or you can use a sensor table. You can see me selecting one of the loaded tables @8:16 - I select another table later in the video for the 8484. If you load a table into the unit then you just use the Freq button and the unit will work out the appropriate cal factor from the table.
Thanks for fast response. I was told that the 478A measured 50 ohms from center pin to ground for termination but label said 200 Ohm Neg for something Do you know what ir should read?
BobZ.
There is a blocking cap on the input side so you should see an open at DC - From the output side, according to the manual you can "...measure resistance between pins 1 & 2, and 3 & 4. The resistance should measure between 1000 and 5000 ohms." (I made a mistake in my first reply with pin 3, should have been 2 - This should measure the thermistor pair on the input, it should be unlikely that the compensation ones have blown).
When the thermistor is connected to the meter they would heat up to be 200 ohms. check out the manual literature.cdn.keysight.com/litweb/pdf/00478-90021.pdf - Figures 5 & 6 as well as paragraph 67.
Thanks for the great video.
I too have a 437B and it's a great tool. I've also got a couple of 435B's and i like their simplicity but not as convenient as the 437B.
I noticed that you didn't switch off the unit while changing sensors. Is that ok?
I'm after the sensor with the +44dBm attenuator attached, but they're quite pricey.
Thanks Roger - Appreciate the comments.
I've had a 435, 436, 437 and I just got a EPM series one - I posted pictures and comments about them here:
www.eevblog.com/forum/testgear/hp-43x-series-power-meters-a-progression-teardown/
I agree with you that the 435B has such a classic look but the 437 is just a better meter in terms of actual usage. In fact while I like the accuracy of the EPM and the range of the sensor I miss the ease of use for the 437.
As for swapping the sensor with the power on, I don't believe that there is any guidance in the manual about that. In fact the turn on procedure explicitly turns the unit on first then calls for the attachment of the sensor (pages 3-7 & 3-8 of the manual). Based on that I've always just swapped them with the meter running.
With respect to the 44dBm sensors, yep costly - I just bought one on Ebay as a gift for my Dad (he's a ham radio operator) and paid close to $450 for it.
@@tgsoapbox I was on your blog and read the information that you presented there, I described on my website without enthusiasm HP-436, in my opinion it is an analogue meter with a digital reading, in my opinion a very interesting construction.
HP-435B is a completely analog device with a great pointer, this meter is currently very cheap about 30 $ has two important points to pay attention to, is very good in tuning and regulation applications, digital meters are not very suitable for this purpose .
The HP-437B has such a small and not precise analog meter, but it is not suitable for tuning, it is not very precise.
The next great feature of the HP-435B is its internal 1 mW 50 MHz power standard.
This is the best model I have ever encountered in my professional practice. It does not react to changes in temperature or changes in the supply voltage, it is very stable and is immediately ready to work after switching on, it does not require pre-heating. no other meter has such a good master power source.
HP-435B was in my studio as an additional source of reference power and as a meter used for regulation and tuning.
In my meter Marconi 6960B I dismantled the original source of reference power and in its place I installed a reference power source with the HP-435B and now I have a very precise meter.
An even better solution would be to use power Marconi sensors with HP-437B, but you would need to develop an interface that would allow it, the HP-437B is a great meter and the Marconi power sensor are great sensors, much better than the HP sensors.
Regards Tomasz
I also had similar fears to connect the sensors to "hot" but I saw on YT how others did so and how it behaves now and nothing bad happens.
You can do it with HP and Marconi equipment, it does not cause problems.
Regards Tomasz
@@sp5mxx That's a nice mod to the Marconi - I have HP Power references in a 435, 438, 8902 and 4418 but I've never compared them to see if the references are different - I just assumed that they'd be the same (or very very similar).
@@tgsoapbox Hello, I still have all the measuring devices that I described on my website, so I made a comparison between all these meters, HP-435B, HP-436A, HP-437B, E4418B, Marconi6960B.
My conclusions are that HP power meters are very good meters, more functional and more convenient than Marconi, while power sensors are definitely better Marconi, HP sensors are not so good.
The reference power sources are better in HP meters, but the absolute best reference power sources, absolutely sensational, are mounted in the oldest HP-435 meter. No other HP meter has such a good reference power source as 435 and the Marconi 6960B meter has a worse source than any meter HP.
Conduct such an experiment, connect the HP-437B or E4418B power meter's power sensor to the internal reference power source and perform the calibration, value 1,000 mW you see on the LCD, leave permanently turned on for a few hours, the result will be a little different, this result will change a little, it will leave, it will not be evenly 1,000 mW, but a bit differently.
After several hours of operation of the meter, permanently enabled on the measurement of the internal reference power source, re-zeroing and calibration, again the result will correctly indicate 1,000 mW, leave the meter turned on for the next few hours, 1,000 mW this time will not change, for that the meter as well as the power source of the reference power are stable and heated.
Turn the meter off for a few hours to cool down well, turn it on again and see that the result will not be 1,000 mW but a bit on the side, do not reset and calibrate it but wait 2 hours and read again on the LCD will be 1,000 mW even though you did not calibrate.
This clearly indicates that these internal power sources require pre-heating before work, so that they do not change the output levels.
Now run another experiment, connect the power sensor to the power source of the HP-435B reference meter and the other end to the HP-437B or EPM power meter and this phenomenon will not occur anymore, turn off and re-enable after a few hours of the external power standard HP-435 it does not cause any difference in reading, it will always be the same or 1,000 mW. The internal reference power source in the HP-435 is perfect and, without any heating, ready for operation and unchanging in time, immediately after switching on it is 1,000 mW and after a few hours of work also 1,000 mW, nothing changes.
It is not so good in any other meter.
Just remember that using an external reference power source, in this case, the external reference power source is the HP-435 meter, zeroing should be carried out with the HP-435 power supply off. Only after the resetting the power supply of the reference power source in the HP-435 should be turned on and the HP-437B meter calibrated.
I do not know if this is understandable?
Regards Tomasz
Thanks for the suggestions but I don't need any more equipment as at 83 I have to get rid of all the acclimated stuff. I also have 5 H-P 487A's that may be open as I can't measure any termination resistance..Don't want to sell anything not workable.
Regards BobzZ
I read around 4.4K between pins 1 & 3 on my 478A when it is cold - If you're reading an open or a short then you're probably right that the mounts are broken.
Hi, Can you do a similar video on HP 438a ?
I have a H-P 8481D Power sensor without the meter. Is there any way to test without the meter? Although it has a 200 ohm load but first has a cap on the input so we can't measure if it is blown Like the old. 478A's. Can you help?
Thanks BobZ
You might be able to jury rig something using a power supply, signal generator and the schematic in the manual but it would probably be easier to just buy a meter (as you said, you can test from the input port so you'll need to try doing it from the FET end). You can get a 435B with free shipping on EBay for around $30-35. You'll need the cable as well if you don't have one so that would set you back another $30 or so.
These things are pretty popular with Ham Radio people so an alternative is to check out the local Ham club and see if they have a regular meeting and ask if someone could bring in their meter to help check the sensor.
I'd offer to do it for you but I'm about to head out on a business trip and will be gone for the better part of a month.
8
sir pls talk about duty cycle in it and usage
Duty Cycle enables you to have the meter calculate what a pulsed input signal peak is. The meter and the sensors are average power measuring devices so a pulsed signal will appear to be of lower power than the pulse actually is. By knowing the signal duty cycle the meter can calculate what the pulse peak is.
Does it measure 5G?
Depends on the sensor that you use - The 8481A does 10 MHz to 18 GHz but the 8482A for example only does 100 KHz to 4.2 GHz. The various sensors will also measure to different power ranges, 8481A is -30 to +20 dBm but the 8481D does -70 to -20 dBm.
@@tgsoapbox Yes one would need sensor and antenna as well, and what I know of these get expensive above the 10Ghz range.As for -70 dBm is 0,012 uW/m2?