Moderators: Dave Moll, Steve Anderson
Steve Anderson wrote:Though others may disagree with me here, basically DO NOT have any bright light and volts applied to the tube at the same time. By bright I mean the average daytime illumination inside the average household. In fact I suggest far less than that, a clear nighttime sky with a full moon can destroy these devices. Of course it varies.
My experience with 931A's has been somewhat disappointing. I found them very sensitive, sure, but at the same time really noisy. In fact useless. These things have been used in the past for decades and with good results, so I can only assume that those I purchased were sub-standard and/or defective. They were cheap though.
A case of, "You get what you pay for."
Steve A.
Harry Dalek wrote:..I can see you need to take care, the ones i won on ebay have the light sensitive area covered by tape can they be damaged while not powered up ?
Steve Anderson wrote:Harry Dalek wrote:..I can see you need to take care, the ones i won on ebay have the light sensitive area covered by tape can they be damaged while not powered up ?
Nope, they're fine as long as they don't have a lot (it varies) of light and volts applied to them at the same time. You can quite safely remove the black tape when there is no volts on the tube. Whoever sold them was obviously unaware of this.
When I say, "A lot of light", think of of a power cut in the middle of the night and no flashlights - that's still a lot of light to these devices.
Remember, these devices are generally blue-sensitive whereas Silicon is red and IR sensitive. I had a blue LED modulated by a really low current (microamps) to test the 931s. The current was so low I couldn't even see the light from the LED after some 15 minutes of my eyes becoming dark adapted. But the PMT sure did! It was actually quite hard to keep out the minuscule amount of street-lighting!
Steve A.
Steve Anderson wrote:Generally PMTs have a response to modulated light into the several hundred of Mhz region. Those developed for nuclear applications (scintillation etc.) go well into the GHz frequencies.
Response to the colour of light and UV varies depending on the coating applied to the cathode and the type of glass used for the tube proper. The datasheet for each type will cover this.
The datasheet often will include a suggested circuit, after a while you'll see that they're all quite similar. I did upload the Burle and Hamatsu handbooks somewhere in the PMT thread but if you can't find them they're here again. Good bedtime reading!
Steve A.
Steve Anderson wrote:As always it's best to refer to each devices datasheet. As a generic species they all generally operate in the same manner, just like transistors as a generalization work in the same way. But each version has different limits and often geared towards a particular application, RF pre-amps, audio output and so on...
The 931A PMT could be said to be the BC107 of PMT's, it's a general-purpose device and finds a home almost anywhere. But if you want hundreds of megahertz a BC107 is not the device of choice. If you want the most sensitivity or lowest noise the 931A wouldn't be the PMT you'd choose.
So study the datasheets, if you're not sure about something, just ask. Hopefully someone here will be able to help.
Steve A.
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