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#1
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VTVM circuit for remote QRO PA monitoring
Looks like an auto ranging circuit would be needed to switch the VTVM to a higher voltage.
That means like a lm3914 in dot mode with one dot set to like 15.05 vdc that dot driving an cd4066 analog switch to the 1,500vdc scale. I'll have to figure the input Z of the lm3914 circuit to fit it in the HV voltage divider. Just hope the 50ua meter movement is slower than the lm3914 and cd4066. 73 de n8zu |
#2
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VTVM circuit for remote QRO PA monitoring
On Thu, 5 Sep 2013, n8zu wrote:
Looks like an auto ranging circuit would be needed to switch the VTVM to a higher voltage. No. You just arrange the "function switch" to put in the right divider as the function changes. For that matter, just put the divider across the circuit being measured, and then the meter just sees the dropped voltage. This isn't a general purpose layout. A test meter is being used for multiple things and often you arent' sure what you will be seeing. But this is a fixed arrangement. A voltage divider there won't cost you anything but a couple of resistors, just leave them there, and over there for that other voltage. Michael That means like a lm3914 in dot mode with one dot set to like 15.05 vdc that dot driving an cd4066 analog switch to the 1,500vdc scale. I'll have to figure the input Z of the lm3914 circuit to fit it in the HV voltage divider. Just hope the 50ua meter movement is slower than the lm3914 and cd4066. 73 de n8zu |
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