Oh, FORGET resistors
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Back to the simple
I am suffering from the day after food binge hangover.
Back to the simple as recommended, my simple bench top function generator and or Fluke 16 DVM are not up to the task. Attempting the simple approach to measuring the output voltage of a resistor bridge circuit the output voltage of the function generator drops as the frequency is increase. I did not even attempt to measure the bridge output voltage. Could be the function generator output voltage drops with increased frequency or the Flule 16 does not do too well with the higher frequency either. Perhaps both.
DT
I am suffering from the day after food binge hangover.
Back to the simple as recommended, my simple bench top function generator and or Fluke 16 DVM are not up to the task. Attempting the simple approach to measuring the output voltage of a resistor bridge circuit the output voltage of the function generator drops as the frequency is increase. I did not even attempt to measure the bridge output voltage. Could be the function generator output voltage drops with increased frequency or the Flule 16 does not do too well with the higher frequency either. Perhaps both.
DT
Now we will try this with all but the volt meter the being same. The voltage meter is a Kesight 6 ½ digit TruVolt.
This time there are better results.
Using 3.015 volts on the output of the frequency generator the output voltage remained steady, only creeping up with frequency 3 or 4 mv’s over the frequency range. The output voltage of the bridge peaked near 11K Hz. Plotting volts on the Y axis, and the Log of the output voltage on a X axis there is the same “bell curve” as noted before.
See the attached pdf.
DT
This time there are better results.
Using 3.015 volts on the output of the frequency generator the output voltage remained steady, only creeping up with frequency 3 or 4 mv’s over the frequency range. The output voltage of the bridge peaked near 11K Hz. Plotting volts on the Y axis, and the Log of the output voltage on a X axis there is the same “bell curve” as noted before.
See the attached pdf.
DT
Hello,
I am scratching my head too. I am not locking in any conclusions. Just conjecture!
Is there something related to phase, inductance or what?
Is there something a RCL bridge with adjustable test frequency will tell? Thinking!
The resistor tested, plotted and posted is a Vishay Dale RN60E2673C. (metal film)
I have tested Carbon Composition, Metal Oxide and Metal Film. When time permits there will be more plots and posts. They all show this bell thing to some degree.
Generally: So far.
The higher the resistor value the greater the peak voltage. The higher the resistor value the lower the peak frequency. The ascending voltage, the peak voltage and descending voltage parts of the bell are all in the audio 20-20K range.
For intermediate vale resistors the ascending voltage measurements are in the upper audio 20-20K range.
For the low value resistors the ascending slope and peak voltage measurements are beyond the audio 20-20K range. (100’s to 1K ohms)
For all the resistor values there is a tail on the curve where the slope of the curve stays relatively flat.
All this is subject to never mind and adjustments with additional testing.
DT
I am scratching my head too. I am not locking in any conclusions. Just conjecture!
Is there something related to phase, inductance or what?
Is there something a RCL bridge with adjustable test frequency will tell? Thinking!
The resistor tested, plotted and posted is a Vishay Dale RN60E2673C. (metal film)
I have tested Carbon Composition, Metal Oxide and Metal Film. When time permits there will be more plots and posts. They all show this bell thing to some degree.
Generally: So far.
The higher the resistor value the greater the peak voltage. The higher the resistor value the lower the peak frequency. The ascending voltage, the peak voltage and descending voltage parts of the bell are all in the audio 20-20K range.
For intermediate vale resistors the ascending voltage measurements are in the upper audio 20-20K range.
For the low value resistors the ascending slope and peak voltage measurements are beyond the audio 20-20K range. (100’s to 1K ohms)
For all the resistor values there is a tail on the curve where the slope of the curve stays relatively flat.
All this is subject to never mind and adjustments with additional testing.
DT
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Yes,
There is a frequency component.
I misspoke the voltage output is the Y axis.
The frequency in Hz is the X axis.
Thanks for asking.DT
Attachments
Try repeating your measurements on a plain 2 resistor divider and then of a 4 resistor bridge.
Use 1,000 ohm resistors.
Hello,
Over months and years I have collected a couple Bankers Boxes full of resistors. Today I pulled out a bag of Corning Glass Works 1% 1K ohm resistors. Per request I assembled a series pair of resistors and a 4 resistor bridge. I also assembled a 4:1:4:1 bridge, as simon7000 calls it. See the photo in post 1928 for a photo of this type assembly.
Back to the frequency generator, as requested by simon7000, I tested and plotted the 4 resistor bridge. Lazy as accused I only plotted only 16 data points, Y axis is output voltage, X axis is Log frequency. This is the PDF.
I also tested and plotted the 4:1:4:1 bridge. This plot is pretts much the same as the 4 resistor plot above. This is the PDF.
I also plotted the voltage measured across one resistor of a 2 resistor series assembly. Such as it is the PDF is here.
DT
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Making the assumption.
I put the 4 resistor bridge back on the function generator and placed the input micro hooks on diagonally opposite corners just as this bridge was tested the last time. The voltage meter probes were connected across a single resistor.
See the attached PDF
All the way up to 40K Hz the plots look the same. Above 40K there are differences and some similarities.
Something is going on in both these plots. Lots of variables!
Thoughts?
DT
Last edited:
When you do two resistors you just measure across the bottom one. When you have a bridge you have two of these. Instead of measuring between the center of both measure each across the bottom resistor.
Currently waiting for some Panasonic ERX5S resistors. They will be used to pad a compression driver (utterly reducing noise floor from output stage instead of reducing volume on dsp). 5w resistors measuring 24*8mm according to spec sheet.
Anyone have experience with these?
Anyone have experience with these?
A positive control should mimic the experimental condition as close as possible and presents a difference that has to be _detected_ .
plots of bottom two resistors.
Same 4 resistor bridge. Now with plots of voltage vs log frequency for the bottom two resistors.
DT
Same 4 resistor bridge. Now with plots of voltage vs log frequency for the bottom two resistors.
DT
Excellent. Now if you take the difference between the readings you will have the data without common mode rejection rate errors.
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