Keithley 2304A high speed power supply

[mrjoda]

yes, heatgun worked very well. Next step is find the source of annoying chirp sound a remove it...

[technogeeky]

I just picked up one of these (for $125 with free shipping). It was in working order, and it appears to operate properly. The only thing unexpected at all is how long it will stay at a elevated voltage before reducing the voltage to meet the current limiting requirements.

The speed of this supply in enhanced mode is absolutely incredible. I'll post some screenshots soon.

In the meantime, a few questions:

1) In what conditions is this power supply able to be used like the famous Keithley SMUs? It seems like it can't reverse polarity (so that's two quadrants out). So I think the leaves:

• source voltage
• source current^[0]
• sink current
• source resistance^[1]

while measuring:

• voltage (with DMM)
• current (direct measurement of source)
• current (with DMM, via current shunt)

I wonder what kind of things this could be used to characterize? It would seem that most/all diodes, some transistors, some inductors, some sensors, etc... could be characterized. Anyone have some cool/unconventional/non-obvious things to try?

2) What do I need to do to protect this unit?

• The 20V isolation from low means that I just need to not try and float the supply on top of some other supply? Anything else to watch out for here?
• What do I need to do to ensure I don't damage the supply when sinking current? Say, if I'm charging a 12V UPS battery with unknown impedance (but presumably low), will this dump e.g. 100A into the unit, or will it limit its own sinking current?
• Anything else to watch out for?

3) Can anyone offer assistance in calibration? The way I see it, there are 2 economical options:

• I borrow someone else's calibration fixtures (paging TiN?  ) and do the calibration with my 5.5 digit Keithley 197.
• I purchase the calibration parts, send them to someone (paging TiN again?  ) to characterize, and calibrate with my 197.

This isn't urgent since I am not sure it's even out of calibration.

Any other tips or tricks?

Besides being a high speed supply, this is also my lowest noise supply (I don't have any linear supplies at all)! Looking forward to it!
^[0]: I would guess that source current means establishing a set current by varying the voltage, which the 2304 can't do, right?
^[1]: The 2304A doesn't have output impedance programming. Which leads me to the last question:

4).
I expected that the parts for this would be unpopulated, but it appears everything anywhere near the output is fully populated. Does this mean we could somehow enable the output impedance stage? Or would it be possible by using the 2303 firmware?

[technogeeky]

Well, some googling and reading and testing has elucidated some things.

1) The 2304a model I have has an analog board which is marked to be one of two units. However, the other unit is the 2303 which is just a lower power version of the 2304a. Neither unit has output impedance control. So that's out.

2) This unit is, if anything, a voltage source. I don't think a voltage source with current limiting acts like a current source (much less an ideal one), so that's out. As is resistance source (see point 1).

3) TiN is in Taiwan, so both options for calibration (for me) are out.

I still would love some perspective on how to think about and how to achieve protection for this power supply, especially when sinking current.

I still would like to hear about what kind of experiments one could conduct using this power supply characterizing things. For example, I powered a white LED and was able to easily see changes in current caused by heating and cooling modulated by touching it with my fingers!

I am going put banana sockets on the front of the power supply, almost certainly. I was wondering about putting a large touch screen LCD on the front of it, but I don't think it's worth it given that this unit isn't quite as versatile as I thought.

[pigrew]

There are two nagging issues with my 2403A that perhaps someone could comment on?

First, is there a way to trigger current digitization other than with a current pulse? I want to trigger the digitization at will over GPIB.

Secondly, mine has firmware A02. One Keithley forum post mentioned it needed a new digital board to upgrade their firmware. Would it work if I stuck in a ROM flashed with a newer firmware? I've run into some unreliability in GPIB when multiple queries are made at once, and I wonder if they were fixed in later firmware. Is the version history posted anywhere?

[alm]

2) This unit is, if anything, a voltage source. I don't think a voltage source with current limiting acts like a current source (much less an ideal one), so that's out. As is resistance source (see point 1).

The 2304A should work fine as a current source. The current regulation specs are specified in the datasheet. Limitations compared to a SMU will be resolution (only down to 1 mA in a single programming range) and possibly output impedance. An ideal current source will have an infinite output impedance (which means a perfect load regulation).

A common problems with using a voltage source with current limit as current source is that the output capacitor, which lowers the impedance of the voltage source, spoils the load regulation as current source. If you set the current source to 1 mA, and connect a 10 kOhm resistor across it, it will charge the output cap to 10 V. If the output now gets shorted, the output cap discharges through the load. Depending on the specifics, this could easily source multiple amps of current (so a 100 000% load regulation) for a few ms. These high-speed power supplies have little to no capacitors on the output (that is how they achieve the high speed), so I would expect them to perform much better as current source.

I wonder what kind of things this could be used to characterize? It would seem that most/all diodes, some transistors, some inductors, some sensors, etc... could be characterized. Anyone have some cool/unconventional/non-obvious things to try?

The 1.25 mA current programming resolution might be limiting for low power devices.

• The 20V isolation from low means that I just need to not try and float the supply on top of some other supply? Anything else to watch out for here?
• What do I need to do to ensure I don't damage the supply when sinking current? Say, if I'm charging a 12V UPS battery with unknown impedance (but presumably low), will this dump e.g. 100A into the unit, or will it limit its own sinking current?
• Anything else to watch out for?

I would also make sure to tie the output to ground somehow if there are other voltage sources involved (connect one of the output rails to ground, possibly via something like anti-parallel diodes to prevent round loops).

It will limit the current it will sink (see datasheet or manual again), unlike the similar half-rack HP/Agilent units. With batteries, I would be worried about the overvoltage protection that might short the output. That could result in some fireworks. I would use a series fuse when connecting it to large batteries/caps, and a series diode when charging.

I would not worry too much about calibration. From what I remember, it requires some loads and measurement of voltage and current that you input into the power supply. A good 5.5 digit DMM should be sufficient for a decent performance verification (if not exactly within factory specs).

[mrjoda]

hello

Look what i found. There is a RJ64 remote port for external remote panel. So i did some test and i found this :

Inside is one ADM202 High Speed, 5 V, 0.1 µF CMOS RS-232 Driver/Receiver.

RJ45 PINOUT
1-2- +5V DC
3 - REMOTE ENABLE PIN - LOG1 activate the remote acces
4 - TX
5 - RX
8-7-6 - GND

RS232 setup : baudrate 9600, 8Bit , Parity none, handshaking none.

With this setup i am getting default response :

Code: [Select]

<0><0><0><0><0><0>?<0><0><0>  ?<0> start response   model INVALID <0>2304A IEEEADR  6A03   00000 50Hz?<0> start response    rev INVALID  ?<0> start response    key INVALID  <0><0> 0.000 V  NL OFF 0.0014 A
I thought it will be SCPI protocol but is not. It does nothing when SCPI commands are sent or return

 

Code: [Select]

?<0>received INVALID    key press
It looks like there must be some button interaction at remote panel and it does not use SCPI but somethink more simple. What do you think ? Does anybody have this remote panel which can be used for data sniffing ?

I would like to made similar panel but with keyboard and rottary encoder because setup of this unit is not very pleasure.

[alm]

I'm pretty sure the front panel of other Keithley instruments like the Keithley 2000/2001 also uses an asynchronous serial protocol. Try to see if anybody (like TiN) has reversed-engineered those, and then check if the protocol for this instrument is similar. You could also check if the built-in front panel also uses the same protocol, and sniff that.

[bitseeker]

I wonder if the protocol might be like that used by older Keithley meters (e.g., 196) when talking via GPIB. It's more compact than SCPI.

[mrjoda]

i think it will be very simple protocol. I tried sent random hex number via terminal and i got only one reaction - 0xE0 enabled output but nothing else. I can't disable it with any combination and i can't change the output voltage.  I will continue with experiments. My plan is write some simple python code (i never use python before so i want to try it) which will contionusly sending ascii table and combination 0x00  to 0xFF and compare new received data with previous for changes. When changes occures it will save combination and received data.

[technogeeky]

I've installed internal connections to three sets of front panel banana jacks. It looks nice. I'm a little worried about noise pickup but it doesn't seem too bad yet, and I can desolder the wires from the output board to test them again later, if I still think it's a problem.

I still need to figure out what mods you guys did to your fans to make them temperature controlled to some extent. Or whatever you guys did.

Any more details?

[mrjoda]

Hi, i am unable to found a source of chirp noise. It is definitely from primary side of power source. Noise disappear when unit is under heavy load.

[TiN]

It's simple UART with few binary codes for stuff like blinking, cursor etc.

3) TiN is in Taiwan, so both options for calibration (for me) are out.

You give up too easy. Shipping little packet with few resistors and connector is not that expensive.

[petarpera]

Keithley 2304a start up with two errors (514 DC calibration data lost and 515 Calibration dates lost). But after start up, do not respond to any button. Tried to set parameter through GPIB - it is recognised but do not accept commands. I checked voltages on test spots, evertything seems to be ok. I would really appreciate any suggestion.

[garrettm]

Hello gentlemen!

I've been hesitant to grab one of these Keithley 2304A high-speed PSUs because of the small screen and wacky connector on the back. However, a good deal recently popped up on the bay and I finally decided to pull the trigger and ended up snagging it for less than $120 USD with shipping.

The listing photos were pretty terrible (a blurry photo of only the front), and I wasn't sure if my unit would come with the rear screw terminal connector or not so I did some looking and think that the original part is made by Phoenix Contact. After getting my unit in the mail, I was pleased to find out it did come with the rear connector installed.

Thinking that I would like to have a spare connector on hand, in case I misplaced the original, I busted out my calipers and did some more looking. The 8-pin connector uses 0.2 inch / 5.08 mm pitch and can be replaced with Molex part number 395340008 "5.08mm Pitch Eurostyle Horizontal Plug, with Retention Screws, 8 Circuits." These are black connectors instead of green, but they are direct replacements for the Phoenix Contact part and, at least for me, were easier to obtain.

Hopefully this helps anyone who is looking for a replacement connector, as many of these units unfortunately come without one installed.

[rl78family]

Hi. What is the difference between models 2304A and 2304?

[alm]

Hi. What is the difference between models 2304A and 2304?

Very little, I think. I skimmed my 1998 paper catalog and compared the specs for the 2304 to the 2304A, and didn't notice any difference. If it helps, I could scan those three pages from the catalog. There might be differences between the circuits, though. I believe the 2304A came out together with the 2303,so it's possible the revision was so the 2303 and 2304 could share more parts.

[rl78family]

If it helps, I could scan those three pages from the catalog.

Thanks, there is no need for this. Thanks for the answer!