Today I wanted to control an AC-Voltage (12 Volts). And I got no signal at all on the screen.
With a multimeter I checked the “Probe” cable on resistance. The “outer” connection (minus) was ok. But the inner connection (plus) had no “through” signal. There must a high resistance or even a cable break somewhere.
I stripped off the Upper Part of the probe including the yellow 10 x resistance switch. So the cable is now naked with the two jacks at both ends. I measured again. Outside ok, inside no signal go-trough.
The cable has not been used for a long time or bent strongly in any wany. Is it possible that there is a “break” of the inner copper-file? Or could it be in one of the jacks?
Do you have any experiences with that problem - and if - a proper solution?
We’re afraid that a scope probe cannot be repaired when defective.
If the unit is less than 2 years old and you still have proof-of-purchase then you can return the probe for inspection/exchange.
If not, the order code for the probe is PROBE60S. It can be ordered from any Velleman distributor.
A cable normally has no break. So it must be one of the connectors. But this seems too difficult to repair.
Will contact a reseller.
EDIT: 19.45
Because I needed to know the voltage on a Low-Volt chain-light (of 6 lamps) in the ceiling of a room, I cut the faulty cable (of my last posting) in the middle, deinsulated the two lines inside and then measured the frequence of the transformator of the chain-light. It was 50 Hz. This seems correct, because the trafo only reduces the volts but keeps the frequence of the net. Then I measured the voltage of the source. It showed 33 Volts on the HPS 140 screen - measured from peak to peak of that sinus wave. But 33 Volts is much too hight for that transformator. It should read about 12 volts. So I took my common multimeter and put it on AC volts: it read 11,9 volts. This seams to be correct. It was expected to be like that.
But why did the HPS 140 read 33 volts? There is no explanation. Even when I half the voltage, because the sine wave has a negative swing, that doubles the voltage reading, that would only result in 16,5 volts.
Can you tell me, what I’m doing wrong? Or is the HPS 140 damaged?
Thank you very much for that contribution to my weak knowledge in such things.
I forgot the Root Mean Square rule. But you are right of course.
I tried to find now on the HPS140 the “rms” feature - and I found 5 slightly different like “Wrms@2Ohms”. Is that the right group of rms-values? But what of those should I use? Or is it not important for my case?
The letter “W”: is that Watts? (cannot imagine, because it’s a voltage)
To follow your advice I needed about 20 min to get the right result. Those tiny tiny little signs on the bottom right side of the screen are not easy to understand, because there is no written “Manual”, where I could find the symbols (double arrow symbol, sinus wave symbol etc.). It’s more a guessing than a real seeing. - And after some weeks or month I can’t remember all that.
Wouldn’t it be good to have a Manual that explains all those litte symbols and signs? I would highly appreciate that. At least me.
I like to chat with you - really. But it would be in some way easier for you to point out a manuskript that holds all that technical “finesse” in a kind of survey.
Sorry, at this time there is no other manual available.
We’ll keep this in mind should we do a redesign of the product.
On Youtube, you can find a couple of movies that show how to use the HPS140 together with our oscilloscope tutor board EDU06.
They are interesting, even when you do not own the EDU06. https://www.youtube.com/watch?v=xwYmpJKaHkE&list=PLyM2aFxOHXOR-t2UKWI1cBcnNg2Rh_-ef
when working through the tutorial manual (pdf) of the “board-experiments” I found some strange behaviour of my HPS 140. I don’t have actually that board. Just reading the manual.
I tried to repeat the experiment Nr. 7 (DC Measurement):
So I put all the settings to the values that have been pointed out in the manual. I did the following:
powered up the HPS 140 from scratch (no probe is connected to the scope)
I set the input coupling to GND
I set the readout to Vdc
The Voltage trace - the straight line parallel to the x-axis - is shown properly. But the height is not correct. It’s too low compaired to the Y-axis. It’s about 1 division too low.
Can you tell me what’s wrong with it? - I ad a jpg-photo of the HPS 140 Screen, so you can controll the settings.
The battery of the HPS 140 is fully loaded and the settings on the Y-axis on the left side seem to be in the middle positions.
But the trace is 1 DIV lower than that middle settings.
Thank you for assistance.
EDIT: I realize now, that the foto is not uploaded. How can I do that?
Try to recalibrate the scope:
1-Switch off the scope.
2-Hold down the menu button and switch on the scope.
3-Now you see CAMLIBRATION on the screen.
4-When the Startup screen disappears, switch off the scope.
Now the dc offset of all V/div steps are recalibrated.
If the trace is not in the center of the screen, there is a hardware problem in the input section.
Yes, the recalibration succeeded. The trace is now exactly in the middle of the y-axis. That’s fine. I’m glad the device is ok.
Thanks for guiding me.
I tried to follow the experiment Nr. 7 in your “EDU 06 Oscilloscope tutor kit” that is called “DC Measurement”. In this tutorial are claimed 3 steps to make a correct measurement of low DC voltages. Sorry, I don’t have the velleman board. So I took a 1,5 Volt Battery (Type AA) to have a certain voltage for measurement.
I understand pretty well the proceedure on page 16 until step 2:
1 - input coupling must be on “DC” (what is autmatically chosen when turning on the device at start)
2 - the readout must be set on Vdc (this must be chosen in the MENU by switching to the 123 values (lower left hand corner)
With that setting I can now measure a 1,5 Volt battery. And it works perfectly. So I could be happy.
But why do I have to do the 3. step (on page 17): “set the DC Reference”. Why should I do that? I can already measure DC Volts with the previous 2 steps. Why should I choose now the “GND” setting? When I select “GND” (that is one of 3 possibilities besides AC and DC) I cannot measure anything. It’s only a straight line on the screen. No voltage is displayed.
Can you help me understand this proceedure on page 17?
When you set the unit to GND for a couple of seconds, it will set the reference to the center of the screen, to make sure that the readout is correct.
Since you’ve just recalibrated, you did not have to do this to get a correct measurement.
May I say: It would have been helpful, if your personal explanation would be part of the official manual on page 17. It took me some time to check out the meaning of that - for me - “obviously” senseless proceedure in step 3. That could be explained better, couldn’t it? The good explanation of a device is very often responsible for the success of a device. I’m shure about it. The HPS 140 could have more users, if the manual would cover the needs of people in a more clearer way.
Everything is working now perfectly again - so far.
