Burleigh WA-20 Wavemeter

[Gabren]

Hello,

The lab I intern recently acquired a 1984 Burleigh WA-20 Wavemeter which seems to be working fine after a little patching. However, we wish to have the wavelength readings sent to a computer, and the wavemeter offers a D-sub 25 pins connector on its back.

In the instruction manuel given by the company, all the pins are assigned a designation. Error are sent as binary values, which are easy to read, but the 7-digit wavelength value is trickier. Indeed, no communication protocol is provided (Bristol instruments, defunct Burleigh successor doesn't have information concerning this issue). 4 pins are dedicated to sending BCD value, while 7 others are to send what I'm guessing to be the 7 digits (see attached file). The BCD values elude me for now.

If anyone has knowledge about communication protocols that could have been used in 1984, it would be greatly appreciated.

As for the bit of reverse engineering I've done, I probed the pins with a reading of the internal reference laser wavelength and all the D0-D6 values gave me the same voltage, as well as the decimal point. The BCDs and other non-binary values (according to my hypothesis) gave

BCD1: 2.533 V
BCD 2: 2,790 V
BCD4: 0.826 V
BCD 8: 1.064 V
D0-D6: 0.49 V
Decimal point: 0.49 V
Load: 0 V
End of Scan: 0.49

The D0-D6 values are odd, since the data to be read should be .632991, and all values were static, suggesting a weird protocol or maybe an electrical bug. Every other value was consistent with the display on the actual wave meter (errors).

Any help would be useful,
Thanks for reading,
Gabriel

 

[Harald Kapp]

Welcome to EP, Gabriel.

How did you measure the voltages? Am I right in suspecting you used a multimeter? This will most likely give you strange and meaningless readings.
The outputs D0...D6 and BCD1...BCD8 are likely multiplexed.
I assume the instrument will put the BCD code for a digit onto BCD1...BCD8, then activate one of D0...D6 to indicate which position this BCD code encodes.
In the same manner the signal 'decimal point' will be active only for the digit selected by D0...D6.

As for the other signals you'll have to do more reverse engineering or find a manual which describes the signals, their function and the timing.

 

[(*steve*)]

Some time ago I bought a very cheap Burleigh high voltage DC op-amp PZ-70 thinking that I could probably find a manual somewhere.

Alas, trying to find *and* information on Burleigh equipment has proven impossible.

I suspect you may be in the same place as me.

Having said that, maybe this is close enough to get some hints from. And see here for where someone else got a manual to an earlier model.

Hey, maybe this is the manual?

 

[Gabren]

Some time ago I bought a very cheap Burleigh high voltage DC op-amp PZ-70 thinking that I could probably find a manual somewhere.

Alas, trying to find *and* information on Burleigh equipment has proven impossible.

I suspect you may be in the same place as me.

Having said that, maybe this is close enough to get some hints from. And see here for where someone else got a manual to an earlier model.

Hey, maybe this is the manual?

Thanks for the reply, the last file is the actual manual for the WA-20, but I already found it online as well as receiving it from the company. It provides insight about the pins, but doesn't go into specifics. Maybe I can salvage info with the more recent manual.

 

[Gabren]

Welcome to EP, Gabriel.

How did you measure the voltages? Am I right in suspecting you used a multimeter? This will most likely give you strange and meaningless readings.
The outputs D0...D6 and BCD1...BCD8 are likely multiplexed.
I assume the instrument will put the BCD code for a digit onto BCD1...BCD8, then activate one of D0...D6 to indicate which position this BCD code encodes.
In the same manner the signal 'decimal point' will be active only for the digit selected by D0...D6.

As for the other signals you'll have to do more reverse engineering or find a manual which describes the signals, their function and the timing.

I did use a multimeter, which was indeed a useless attempt at getting a first glance of the communication outputs. Great hypothesis, I was somehow thinking BCD values were encoded on 3 bits and not 4. I'll probe the pins again with appropriate apparatus.

 

[Harald Kapp]

BCD = binary coded decimal. To encode ciphers from 0 to 9 you need 4 bits (3 bits are sufficient for cihers from 0 to 7 only).