Altek 334 4-20mA Loop Calibrator

[Cones]

Hi,

Another piece of equipment that I have bought on ebay recently. An Altek 334 4-20mA Loop Calibrator.

If you are not familiar with 4-20mA process loops they are used extensively in control automation. The 4-20mA loop signal is perfect for long runs to sensors, actuators and inverter drives. It can source the 4-20mA to simulate a powered sensor or a control signal. It also has a 2 wire mode to simulate a 2 wire loop powered sensor. It will also work in both 4-20mA mode and 0-100% which is easier if you are testing signals to control equipment. As a bonus it also has a 0-100 VDC voltmeter function, so you can test the loop supply voltage on a 2 wire system.

I was pretty sure it was going to be broken as it only sold for £21.50 and these are around $950 new. Although the new model is slightly different to this one.

But a quick replacement of the three 9v leaky batteries that came with it and it proved to be almost spot on with my Fluke 179.

It looks like this one was made in 08 1993 so pretty impressed that it is still working nearly perfectly after 20 years!

The croc clips are a little rusty, and the 4mA-Adjust-20mA selector switch is a bit floppy in the middle position and could perhaps do with replacing.

I'd be interested in the calibration instructions or a circuit diagram if anyone has them please?

Anyway a few pictures for those interested.

[Cones]

A few more pictures.