A description of how to do this is in the attached PDF. Please accept apologies for submitting it like this, but I do not know how to do it otherwise.
Since writing this document I came across a post that told about "Phantom power" from the sound card mic input connector. That is something I never knew about so I did some extra "snooping" at the mic input of my Compaq laptop. I use a DT830D DMM for my measurements. When there is no recording device active on the PC, there is no output from the mic connector. When a recording device is active then 3.6 volts (no load) is measured. The short circuit current is 800uA (800 micro amps). This can be used to monitor relay contacts without connecting anything to the electronics. A 33K resistor across the relay contacts and a 100K resistor in series with the signal to the PC gives me suitable differential pulses. There is a little noise and contact bounce, but not bad enough to affect my time measurements.
I am pretty keen on writing the application to measure delays similar to a lap timing stop watch. It would measure times between the same polarity pulses, or (eg) between a positive and a subsequent negative pulse. The display would be a table of successive readings so that the observer can see changes in times while adjusting for calibration.
Please can someone tell me how to trap those pulses as events in a VB or VBA application? With that information I will write the application and make it public to anyone interested.
Kind regards and best wishes to all over the festive season.
Since writing this document I came across a post that told about "Phantom power" from the sound card mic input connector. That is something I never knew about so I did some extra "snooping" at the mic input of my Compaq laptop. I use a DT830D DMM for my measurements. When there is no recording device active on the PC, there is no output from the mic connector. When a recording device is active then 3.6 volts (no load) is measured. The short circuit current is 800uA (800 micro amps). This can be used to monitor relay contacts without connecting anything to the electronics. A 33K resistor across the relay contacts and a 100K resistor in series with the signal to the PC gives me suitable differential pulses. There is a little noise and contact bounce, but not bad enough to affect my time measurements.
I am pretty keen on writing the application to measure delays similar to a lap timing stop watch. It would measure times between the same polarity pulses, or (eg) between a positive and a subsequent negative pulse. The display would be a table of successive readings so that the observer can see changes in times while adjusting for calibration.
Please can someone tell me how to trap those pulses as events in a VB or VBA application? With that information I will write the application and make it public to anyone interested.
Kind regards and best wishes to all over the festive season.
Attachments
-
365.1 KB Views: 15