New Keysight Agilent U3401A Bench Multimeter

I recently purchased a new multimeter for use in the lab. I have two handheld digital multimeters but having a bench meter would work for me quite well to save me from reaching for the handheld and finding space for it when i'm working on something.

The Keysight U3401A is a budget / entry level 4 1/2 digit DMM from Keysight, although lacking in some features it will be fine for my needs and even this entry level offers me some technical advantages over my handheld meters. Most notably; higher voltage (upto 1.2kV) and current ranges (upto 20A), greater accuracy and resolution across the board. Voltage is 0.02%+4, current 0.05%+4 or 5 depending on range, resistance 0.1%+3 or 6 depending on range.

The Keysight U3401A was purchased through a member of the EEVblog forum for exactly £200.00 including shipping, as a customer return from Element14. The unit is within calibration and under manufacturers warranty, even the test leads had not been opened. Of course this was a one-off deal.

The new Keysight U3401A DMM sat on top of my two Hewlett Packard 6632B DC Power Supplies (aka Agilent then Keysight!) next to my faithful Xytronic LF-1000 soldering station.

My current two meters are:

Sinometer / Mastech MAS-343 with tape to prevent changes because this is exclusively connected and used with my Testec HVP-40 high voltage probe.

Fluke 107, a budget meter aimed at the Asian markets. It's a great value meter and one i would highly recommend to beginners who need something reasonably priced but built well and one that meets it's safety specifications.

Next Teardown: Perkin Elmer LS5 Luminescence Spectrometer

Fresh from ebay, wheeling the latest lump into the shed! Might be a week or so before you see this one attacked with a screwdriver.

Liquid Scintillation Analyser Parts Haul

While i still need to take a more detailed look at the sample loading and electronics for the Packard 1000 TR Liquid Scintillation Analyser i thought i would do a quick update listing out the total haul from this.

So the analyser itself was bought off ebay from a seller local to me so there was no shipping, which would have been a problem otherwise due to it's weight any shipping costs would have been a problem.

I salvaged:

• 1* 5000v AC power supply.
• 2* Hammamatsu R331 Photomultiplier tubes.
• 1* Dual channel adjustable photomultiplier power supply.
• 1* Radioactive source for my collection.
• 1* 2*40 LCD Module
• 64Kg Lead for recycling @ today's price it's just under £1.00 per Kg. I saved about 20Kg for  myself so i can store my radioactive samples.
• Approx 10kg of other recyclable metals; steel, aluminium & brass.

Hopefully over this coming weekend i will be able to finish looking at the electronics and that sample load/unload mechanism. Though i dont expect to find anything more salvageable.

Testing a 5000v Power Supply (Neon Sign Transformer)

I took a quick look at the power supply that was used for the ionizer in the liquid scintillation analyzer. It's a Chapman brand 120v input with 5000v output. I believe this is essentially a neon sign transformer with integral ballast/current limiting.

After removing the electrodes i just wired it into my variac to run it upto it's rated 120v input and positioned the output close to the ground wire for some sparkly action. The output is dead on 5000v AC with an input voltage of 120v.

This should make some interesting videos in the future. Especially if i can find some things to zap and also increase the input voltage beyond the 120v rating.

Modifying a Packard / Perkin Elmer Photomultiplier PSU

Today i took a deeper look at the packard photomultiplier power supply i removed from the LSA i recently took apart. It has a Packard part number of 7101139.

I wanted to test powering on the PSU from my bench power supply and verify the function of the control input. To allow me to easily use this in future projects. When installed in the 1000 TR LSA 5v was seen on the two input pins which seemed to enable the power supply output at around 1600v.

First i verified the power supply was working. Applied +15v to the power input and +5v to the control line and got the +1600v output i had seen when the unit was in the LSA.

After inspecting the circuit i spotted a MAX584 voltage reference  close to the input with only the 10v output of the reference in use i suspected the board would be adjustable so altered the voltage between 0 and 10v and indeed the supply did alter it's voltage from +970v to +2290v.

I wanted to check the circuit to see if it can be made more stand-alone and still be made adjustable, there are missing trimpots and jumpers on the PCB so wondered if these would allow this.

On closer inspection JMP1 & 2 had a soldered link across two of the three pads with JMP3 unpopulated. These connected the inputs on the control cable connector to the rest of the circuit. In the other position they connected in the two missing trimpots R41 and R42 into the same input.

The pads were cleaned of solder, three pin headers installed and using a salvaged 10kohm trimpot the trimmers allowed full voltage adjustment from +970v to +2150v on each channel. Switching of the JMP3 jumper allows both channels to be turned on or off, but not independently. I maybe able to further modify this two allow that feature.

Soon i will sort out a suitable enclosure, probably with an integrated power supply for connection to the mains and two 10 turn pots to allow voltage adjustment.