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Problem with 15 resistors in a series

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sanna

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Hi, I have connected 15 resistors in series and every resistor is 10 M ohm, But when I measure it I don't have 150 Mohm. I tested and saw that it comes up to 53 Mohm at resistor number 8 and from resistor number 9 begins to reduce. I don't understand why?
 

onion456

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resistors

you have absolutely nothing in parallel with these resistors?
 

sanna

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Re: resistors

yea I have a 100 pF capacitor. It is a charge amplifier set to 100 pF feedback, 0.1 Hz lower limiting frequency, 10 Hz upper limiting frequency, and +20 dB gain.
 

doho

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Re: resistors

sanna said:
yea I have a 100 pF capacitor... .
Could it be that you are measuring the leakage of the capacitor?
 

echo47

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resistors

If the resistors are connected to an amplifier, then your ohm-meter's test current may be flowing into the amplifier's input.

Or maybe your ohm-meter isn't designed to measure such high resistance values.
 

hbaocr

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resistors

please check resistance I/O of your multimetter.If the resistor is not more than about 10*(the resistor you measure).Your result receive maybe not right.In this case I think the resistor you need to measure is too large.But the resistance I/O of mutimetter is smaller.Two resistor is parallel ,it make the measured resistor reduce
 

_i386sx25_

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Re: resistors

I think 150MOhm is too high to measure with a ordinary battery powered multimeter reliably. A higer voltage measuring system would be nice. Beside since resistance too high, any dirt or humidit on PCB, even if the pcb coated with solder resist, will effect the resistance.
 

ubna

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Re: resistors

There can be nothing like pure capacitance.every capacitor has some resistive component too. Here since your capacitor is in parallel with high value resistors there is a fall in the resistance.
 

barry14

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Re: resistors

Another possiblity is the resistance due to your body. Are you making the measurement by holding the meter probes with your hands? Try to connect the probes without any body contact.
 

madhoc

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Re: resistors

your measuring instrument could be the problem. Remember 150M is very high resistance. Please confirm that the meter you are using can measure this resistance and that the knobs or buttons are properly set.
 

pinoy

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resistors

Can you post your circuit? the input impedance of your amplifier may contribute it. Remember your resistance is very big. 150Meg. Or the leakage current of your capacitance.
 

smith123

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Re: resistors

you shoud check the circuit by high level instrument devise
 

ibeanjacob

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Re: resistors

It is most probably because your multimeter just is not designed for measuring such high resistances.
You need specialised meters and setup to measure such high resistances
Check the specs of your meter.
My sanwa meter measures only upto 30Mohm.
Another cheap chinese one measures only upto 2Mohm.

And also dont catch both ends of resistor being measured with your hands,what will happen is your body resistance which is a few Mohms will come in parrallel and distort the reading.
 

selvaraj_iit

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resistors

The resistance measuring meter you are using is not capable of measuring 150 Mohm. Choose a suitable meter and then measure. It will definitely show 150 MOhm.
 

yqyhaohan

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resistors

if these 15 resisters are on the circuit board, it's normal to have 53M ohm, because the resistance you got is not the 15 resistors, but the other part of the board
 

Andrew8611

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Re: resistors

I think it happens because the output resistance of your ohm meter is close in value to the 150 MΩ, so when you try to measure you will get a parallel between the two and the result will be incorrect, try using a meter with a higher output resistance
 

hdrzaman

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resistors

im not getting ur point
 

emadi

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Re: resistors

they may be loaded from another way
 

hdrzaman

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resistors

there might be somthing short circuited
 

sbalpande

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resistors

It is most probably because your multimeter just is not designed for measuring such high resistances.
You need specialised meters and setup to measure such high resistances
Check the specs of your meter.
 

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