This is not a request for help, it is more of a show and tell.
I have commented several times here on ETO, that my bench DVM and frequency counter both have a GPIB (General Purpose Interface Bus) built in.
This allows a PC with a suitable control program to control the instruments and automatically record the measured values over a period of time.
I have made good use of this facility several times, for example when I was building a NiMH battery charger and when I was building a frequency stabiliser for an old shortwave receiver (uses valves, it is that old).
With this setup I can measure voltage and frequency, one of each type of point.
The thought then occurred to me that it would be useful to be able to measure several frequencies or voltages at the same time, or rather one after the other very rapidly.
I needed a multiplexer of some kind.
It would also be useful to be able to switch things as part of an automated test, and also determine the state of somethings, on or off.
So one day I had a look on eBay and found a GPIB digital I/O board and bought it.
64 bits, opto isolated, some inputs and some outputs, just the job.
The next problem was how to mount the thing.
I had a cabinet with a rack which could be adapted to hold that card, I went as far as building it up and mounting a power supply in the case. But the problem remained of how to implement the connections to the outside world, and the case really was far too big. I even bought another case, but it was awkward to mount the card and again it was just too big.
I bought a couple of prototyping boards of the same size as the digital I/O board, and some relays and connectors, but what to use for a case?
One day I was idly looking at a pile of junk under a table and realised that I had a nice case which had contained a satellite modem (I had bought the modem very cheaply for bits).
Even better, the DIO board and the proto board fitted exactly into slots in the extruded alloy case.
So, I built up an I/O interface board with connectors to the outside world, relays for the DMM and Counter multiplexer, a couple of integrated circuits for logic to drive the relays, lots of wire to connect to the digital I/O board, and the result is this:
Put a three terminal regulator for the +5v supply into the bottom of the case, (makes for a good heatsink).
Assemble the whole lot and it looks like this:
The cable snaking off out the back of the case is a GPIB cable. They are a bit odd if you have not seen them before, the connectors have both plug and socket so that they can be stacked to allow the cable to daisy chain from one instrument to the next.
Put the lid on and the overall appearance is as we see here:
I did not put on a front panel because that is where to connections to the equipment under test come into the box through the green connectors.
The top of the case is not fixed, it will easily slide off to allow access to the inside of the box, should that be necessary when making the test connections.
So there it is, that is what I have been doing for the past two years since I first thought about it.
All I need now is some project which need lots of measurements...
JimB
I have commented several times here on ETO, that my bench DVM and frequency counter both have a GPIB (General Purpose Interface Bus) built in.
This allows a PC with a suitable control program to control the instruments and automatically record the measured values over a period of time.
I have made good use of this facility several times, for example when I was building a NiMH battery charger and when I was building a frequency stabiliser for an old shortwave receiver (uses valves, it is that old).
With this setup I can measure voltage and frequency, one of each type of point.
The thought then occurred to me that it would be useful to be able to measure several frequencies or voltages at the same time, or rather one after the other very rapidly.
I needed a multiplexer of some kind.
It would also be useful to be able to switch things as part of an automated test, and also determine the state of somethings, on or off.
So one day I had a look on eBay and found a GPIB digital I/O board and bought it.
64 bits, opto isolated, some inputs and some outputs, just the job.
The next problem was how to mount the thing.
I had a cabinet with a rack which could be adapted to hold that card, I went as far as building it up and mounting a power supply in the case. But the problem remained of how to implement the connections to the outside world, and the case really was far too big. I even bought another case, but it was awkward to mount the card and again it was just too big.
I bought a couple of prototyping boards of the same size as the digital I/O board, and some relays and connectors, but what to use for a case?
One day I was idly looking at a pile of junk under a table and realised that I had a nice case which had contained a satellite modem (I had bought the modem very cheaply for bits).
Even better, the DIO board and the proto board fitted exactly into slots in the extruded alloy case.
So, I built up an I/O interface board with connectors to the outside world, relays for the DMM and Counter multiplexer, a couple of integrated circuits for logic to drive the relays, lots of wire to connect to the digital I/O board, and the result is this:
Put a three terminal regulator for the +5v supply into the bottom of the case, (makes for a good heatsink).
Assemble the whole lot and it looks like this:
The cable snaking off out the back of the case is a GPIB cable. They are a bit odd if you have not seen them before, the connectors have both plug and socket so that they can be stacked to allow the cable to daisy chain from one instrument to the next.
Put the lid on and the overall appearance is as we see here:
I did not put on a front panel because that is where to connections to the equipment under test come into the box through the green connectors.
The top of the case is not fixed, it will easily slide off to allow access to the inside of the box, should that be necessary when making the test connections.
So there it is, that is what I have been doing for the past two years since I first thought about it.
All I need now is some project which need lots of measurements...
JimB
