How they made 400 Vdc shift ?? !!

[ahmed osama]

hii all

now i saw a commercial prof. oscilloscope and test something in it

i input 10mV AC signal + 300 Vdc OK and i set the V/div to 100 mV , So ofcourse nothing appear except a yellow line in top of screen which mean that the signal is out of the choosen scale so inspite of change V/div to 300 V , i kept to rotate the POS button till i got -300 Vdc shift and i saw my signal on 100mV V/div

now how they made such Osc. !! do they generate a 300 Vdc !! and add it & what op-amps can add that ??

Plz can any one tell me what is the trick here???

thanks

alot

bye

 

[humber]

There are many ways to provide the offset without the need for a 400V source, or amplifers that can operate at that level. For example, consider a "virtual ground" amplifer, where currents, rather than voltages are summed.

Perhaps Ian Hickman's book may provide you with the answer.


'Oscilloscopes How to use them, How they Work'



Humber

 

[pradeep.bhardwaj23]

How we make High Voltage In Electronic circuits eg 400v then we are actually making use of Clamping Circuits that are having Diodes and Capacitors.
Any basic electronic book have clipping and Clamping circuits Knowledge.
Find out in your text book

 

[ahmed osama]

How we make High Voltage In Electronic circuits eg 400v then we are actually making use of Clamping Circuits that are having Diodes and Capacitors.
Any basic electronic book have clipping and Clamping circuits Knowledge.
Find out in your text book

my ques. wasn't how to make 400 V , my ques. does they generate such 400 v or there is a more simple way ..

and as you see , the last reply saying that you cad add a currnet to a suming op-amp ct which asif it is from 400 V dc source and cancel the other one ...

thx all
bye

 

[robust86]

maybr use from autotransformres that durppas dc value

 

[grittinjames]

they r not going to generate 400v ,but you know signal applied is to y plate of osciloscope.they will be doing some adjment there ,

 

[XNOX_Rambo]

Did you measure with a 10:1 probe?

 

[shg]

All oscilloscopes i've seen had a AC/DC switch. In AC position it introduces a series capacitor in signal path, which decouples DC component. That makes AC signal + DC bias measurements quite easy.

It's a bit (or sometimes "a lot") harder to remove high voltage AC component, or to measure DC voltage with DC bias, but it's not impossible, usualy this is done using a differential amplifier with one input connected to "bias" voltage and the other one to measured voltage (which is bias + signal). It's quite useful for performing measurements in line supply equipement, when one can't guarantee that ground point in oscilloscope and device will be at the same potential. In such a situation one of oscilloscope inputs (B) is connected to device's ground, and the other one (A) to signal point, the oscilloscope should be switched then to A-B (differential) mode.

 

[Kral]

ahmed osama
The Pos control on an oscilloscope provides offset to the vertical display, but the offset is not necessarily equal to the equivalent DC input. The display offset is added at a low level point.
Regards,
Kral