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Question: What are these things? (AKA chemist trying not to be electrocuted)

Hello all,

Here is my set up, I have 8 photodetectors, I assume they are in fact photoresistors but am not sure. I have not been able to get a resistance measurment when I put a multimeter across it, but I get a voltage when I touch both probes to the hot wire.

These photo-thingagigs connect to what I assume is a constant current supply. As best I can figure the current supply corrects for noise in the line(actually I use a knob on the front to correct for noise) and as the resistance of the photoresisters change the voltage output of the current supply changes to maintain a constant amperage. A data logger captures the change in voltage and I use this data to analyase and compare different samples. If it help this assumes that as the light hitting the resistor decreases the resistance increases and forces an increase in voltage.

Here of course is the kicker, this piece of equipment was cobbled together by our field service group. Nobody here is willing to touch the thing, and I am down to a single working photodetector. I dont know if it is likley to be the current supply or the photoresistors(assuming of course that they are photoresistors), or for that matter the datalogger or the datacapture software.

My best guess is that I am using photoreistors and they have burnt out due to time and use. Is this something anyone has seen before? And since I have been unable to get a resistance reading off of the working sensor, what am I missing? Is the resistance from a standard photoresistor to low to measure with a multimeter, I wouldn't think so, but God knows I have been wrong before.

Any help appreciated.

Ghostwriters

Reply to
ghostwriter
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Well, i have been an electronic technician for over 50 years, and can say that, for all practical purposed that you know almost nothing about electronics or electronic components of any type. At least someone pointed to one box and said "this is a power supply" and the detectors and said "these aer photodectors". And you have "dug into the guts" enough to be "dangerous". From your description, i cannot say if you have photoresistors, photodiodes, or some other tyoe of photo detector. The same goes with the supply, except it is rare to find a constant current supply in use. The "nobody is willing to touch it" would seem to mean that they know less than you do. And if the equipment is slowly falling apart and there are no local repair options in sight, then it would seem that you are beating a dead horse.

You give no clues as to the use(es), sensitivities, spectral needs, or any thing else of interest - except the hint that it has some kind of data digitizing capabilities, which something else then reads, logs and maybe analyzes (clue: software). I most likely could fix it, and maybe even find a more reliable way to do the same detection. However, either trash it and get off-the-shelf equipment to do the job, or forget the whole thing and let someone else "worry" about the dead project (it is dead if the equipment is dead).

Reply to
Robert Baer

On a kinder note, this discription could be for almost any type of a solid state photodetector. It would be helpful if you could take some pictures, post them on a web site, and let us know.

Otherwise are there any part numbers on the photodetectors?

Best regards mark

ghostwriter wrote:

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Mark W. Lund, PhD            ** Battery Chargers
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Reply to
Mark W. Lund, PhD

Very true, 90% of my knowledge in the subject is electrochemical theory and the remainder is dominated by black box understanding of the capacities of electrical equipment.

They are in fact photoresisters. And after finding a meter with a high enough resolution I was able to determine that they had in fact worn out due to use. I realized that since my small multimeter was reading an open circuit that I needed to go up in resolution not down. Exposure to varying levels of light let me create comparison curves and at that point it was obvious that the problem was in the photoresisters.

Again true, it is a constant voltage supply, wired so that a variable resister can be used to remove noise from the line then run though a digital Amperage meter that generates a voltage signal that is captured by a datalogging card and sent into a NI Virtualbench data management suite.

I have ordered the photoresisters and will wait to see how it goes from here.

No real need to know too much about the details, I will replace the resisters with the same make and model. I am primiarly interested in doing control/experimental comparisons and therefore do not have specific specs for the results. If they are far removed from the older results I will lose the ability to do cross-comparison between old and new data, not a huge loss for me.

However, either trash it and get off-the-shelf equipment to do the

Thanks for the reply.

Ghostwriter

Reply to
ghostwriter

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