Purchased a used 2015 some time ago from Parts Connection, which is a reliable supplier. I'm trying to use the interal signal generator to check a weak channel on my tube amp. Followed the instructions, but I can't seem to get a stable signal from the signal generator.
Any thoughts from those that have a 2015? Regards, Bill
Any thoughts from those that have a 2015? Regards, Bill
Hi Kevin. Yes it was me, back in 2003. I designed the audio generator and audio distortion measurement circuitry and defined the distortion measurement algorithm. It was designed to measure distortion of early cell phones on the production line, not extremely low THD of high end audio. It should be fine for looking at the even harmonic distortion that most tube amplifiers generate.
So, how are you using it? Front panel, or GPIB? Please explain what you have done, and in what order.
So, how are you using it? Front panel, or GPIB? Please explain what you have done, and in what order.
Hello,
@Kevin thank you very much for forwarding the message. Popups have kept me from responding sooner.
I'm using the front panel. I followed the manual directions for the THD set up to program the signal (sine wave). When I exit the setup the panel meter reading is unstable. Thank you very much for the help.
Best Regards and Happy New Years. Bill
@Kevin thank you very much for forwarding the message. Popups have kept me from responding sooner.
I'm using the front panel. I followed the manual directions for the THD set up to program the signal (sine wave). When I exit the setup the panel meter reading is unstable. Thank you very much for the help.
Best Regards and Happy New Years. Bill
Need a lot more detail, step by step. For example, how are things connected electrically, did you connect the generator output to the front panel input? Did you connect the generator to the amplifier input and connect the amplifier output to the generator?
I would like to see lots of text, exactly what is connected to what, and what front panel buttons were used in the exact order they were used.
I no longer have a 2015, so aside from the Rev F manual I just downloaded, I am doing this from 15 year old memories.
I would like to see lots of text, exactly what is connected to what, and what front panel buttons were used in the exact order they were used.
I no longer have a 2015, so aside from the Rev F manual I just downloaded, I am doing this from 15 year old memories.
Happy New Years,
I'm out of town and will put together a detailed list this week. Thank you, Bill
I'm out of town and will put together a detailed list this week. Thank you, Bill
Hi Glenn, I'm playing nowadays with Keitley 2015 too and I try to figure out if the generator part can be improved a little...
Closed loop (straight cable output-input) renders in my case 0.025% THD. I've analized the signal from generator alone by the means of a decent soundcard (Focusrite Scarlett 2i2 2nd gen) and the THD figure looks about the same, around 0.025%.
So, my question is if something can be done on the analog side of the generator in order to decrease the distorsion?
Closed loop (straight cable output-input) renders in my case 0.025% THD. I've analized the signal from generator alone by the means of a decent soundcard (Focusrite Scarlett 2i2 2nd gen) and the THD figure looks about the same, around 0.025%.
So, my question is if something can be done on the analog side of the generator in order to decrease the distorsion?
My guess: the Generator Performance is limited by the DAC resolution. No decent analog circuitry is "that bad".
Hello,
I have a problem with Keithley 2015 THD. On the first output of the generator, I do not have a sinusoidal signal, but on the second channel I have both a sinusoidal signal and pulse (of course, switched not at one time). What could be the cause of the fault? Is there any service documentation with diagrams of this meter available? Where and what should I measure?
I bought this meter as used. I wonder if by connecting a signal from the generator to the tested equipment and at the same time having a connected oscilloscope, with a short circuit with a PE wire, it can work correctly? Could such damage occur as a result of a short -circuit of the negative potential of the generator with the Protective Power of the PE? The easiest way to write a question is: can the generator output sockets be connected directly to the PE protective cable? Because I noticed that they are factory isolated from the metal parts of the meter housing and probably for a specific reason.
Thank you very much for the answer and if possible, please send it to the email address: ogiman@poczta.onet.pl
Greting
Aleksander
It has been 18 years or so since I designed that, so things are a bit hazy. As I recall the direct digital synthesizer had both a square wave and sine wave output and that is what I used. Nothing on the sine output but both on the pulse out? Sounds like, maybe a bad connection to the BNCs on the back.
Thank you for your response.
As I wrote in the above message, surprisingly on the second channel I have both mileage sinusoidal wave as well and rectangular (of course not at the same time but after changing in the settings). On the first channel I do not have a basic sinusoidal signal.
I have three question:
1. Is there any service documentation with diagrams of this meter available?
2. Could such damage occur as a result of a short-circuit of the negative potential of the generator with the cable PE of supply installation 230V from from the BNC oscilloscope socket (apart from additional implemented distortions from oscilloscope with in such a connection configuration)?
3. Can the generator output sockets be connected directly to the PE protective cable? Because I noticed that they are factory isolated from the metal parts of the Keithley housing and probably for a specific reason.
Thank you very much for the answer
Greting
Aleksander
As I wrote in the above message, surprisingly on the second channel I have both mileage sinusoidal wave as well and rectangular (of course not at the same time but after changing in the settings). On the first channel I do not have a basic sinusoidal signal.
I have three question:
1. Is there any service documentation with diagrams of this meter available?
2. Could such damage occur as a result of a short-circuit of the negative potential of the generator with the cable PE of supply installation 230V from from the BNC oscilloscope socket (apart from additional implemented distortions from oscilloscope with in such a connection configuration)?
3. Can the generator output sockets be connected directly to the PE protective cable? Because I noticed that they are factory isolated from the metal parts of the Keithley housing and probably for a specific reason.
Thank you very much for the answer
Greting
Aleksander
1. I haven't worked for Keithley since 1999, so I don't know what there is. It is almost certain that they will not share schematics, and I don't have any.
2. Not sure about this short you refer to in question 2, but the 2015's circuitry is isolated from mains via a transformer with a triple faraday shield, so it probably would not cause damage. I'm not clear about what a PE is. Could you attach a sketch of the setup you had?
2. Not sure about this short you refer to in question 2, but the 2015's circuitry is isolated from mains via a transformer with a triple faraday shield, so it probably would not cause damage. I'm not clear about what a PE is. Could you attach a sketch of the setup you had?
@glen F
I sent my unit to Custom Calibration Solutions, LLC in Oregon. Dave found an issue with one of the boards. He sent it to the shop in Florida where it was repaired and calibrated. Dave went out of his way to help me and the cost was more than reasonable.
As you know, the 2015 thd is also a very good voltmeter and has four-wire resistance measurement capability. Dave got the four-wire measurement calibrated to a nats eyelash. Regards, Bill
I sent my unit to Custom Calibration Solutions, LLC in Oregon. Dave found an issue with one of the boards. He sent it to the shop in Florida where it was repaired and calibrated. Dave went out of his way to help me and the cost was more than reasonable.
As you know, the 2015 thd is also a very good voltmeter and has four-wire resistance measurement capability. Dave got the four-wire measurement calibrated to a nats eyelash. Regards, Bill
With the new ownership of Keithley more info is available: https://www.tek.com/en/manual/digit...2015-series-thd-and-audio-analysis-multimeter There is also lots of discussion here: https://www.eevblog.com/forum/repair/keithley-2015-dmm-repair/msg3546684/#msg3546684 EEVblog has many other discussions as well. And there are details here under the 2015 and 2016 subheadings: https://xdevs.com/doc/Keithley/
My 2015 works fine but I want to be prepared. And I would love to upgrade the firmware to 2015-p but that may not be possible.
Hello,
Hello,
I am sending a primitive scheme that I was able to do. I hope that it will see how the connections look like.
Namely:
1. Keithley sinusoidal signal outputs are connected to the input of the audio amplifier. One to the right channel the other to the left canal.
2. The audio amplifier signal outputs are connected analogously to the Keithley left inputs to the first right to the second.
The last connection or oscilloscope is troublesome. The same audio amplifier signal outputs are connected to the first and second oscilloscope channels to track the shape and level of the test signal generated by Keithley when measuring harmonic distortions.
The construction of the amplifier is made in such a way that the mass of the input audio signal and the output mass and the metal housing of the amplifier are connected together and are on the same potential.
The supply of an audio amplifier is a two -wire (flat plugin without entering the plow) and the PE protective cable is not supplied to it.
This is the opposite of the oscilloscope supply where the power socket borea is connected directly with the BNC socket screen.
In Keithley, the entrance and output nests are fully isolated from the Earth and the PE protective cable.
And now we reach the main point of the topic: by connecting an oscilloscope to the output sockets of the audio amplifier (for imaging the shape of the test signal) at one moment "I ground" and cause a short circuit to the PE cable power socket 230V, all BNC cables from the Keithley generator and masses of input and signals output audio amplifier and its metal housing.
Am I then able to damage the Kethley Audio amplifier generators and how does this affect the measurement of distortion?
Hello,
I am sending a primitive scheme that I was able to do. I hope that it will see how the connections look like.
Namely:
1. Keithley sinusoidal signal outputs are connected to the input of the audio amplifier. One to the right channel the other to the left canal.
2. The audio amplifier signal outputs are connected analogously to the Keithley left inputs to the first right to the second.
The last connection or oscilloscope is troublesome. The same audio amplifier signal outputs are connected to the first and second oscilloscope channels to track the shape and level of the test signal generated by Keithley when measuring harmonic distortions.
The construction of the amplifier is made in such a way that the mass of the input audio signal and the output mass and the metal housing of the amplifier are connected together and are on the same potential.
The supply of an audio amplifier is a two -wire (flat plugin without entering the plow) and the PE protective cable is not supplied to it.
This is the opposite of the oscilloscope supply where the power socket borea is connected directly with the BNC socket screen.
In Keithley, the entrance and output nests are fully isolated from the Earth and the PE protective cable.
And now we reach the main point of the topic: by connecting an oscilloscope to the output sockets of the audio amplifier (for imaging the shape of the test signal) at one moment "I ground" and cause a short circuit to the PE cable power socket 230V, all BNC cables from the Keithley generator and masses of input and signals output audio amplifier and its metal housing.
Am I then able to damage the Kethley Audio amplifier generators and how does this affect the measurement of distortion?
