Precision Resistors HELP!

[Dennis]

I am in need of a 9.5 ohm and 90 ohm precision resistors for
Multi-meter repair. Does anyone know where I can find these
resistors? I not beyond series or paralleling resistors to get the
ohmic value.

Thanks.

 

[Sheldon Cribb]

Did you try Digi-key? http://www.digikey.com

 

[Sofie]

Dennis:

If you can gain access to a good quality DMM.... hopefully 4 or 5 digit you
can usually find an off-the-shelf 10 ohm resistor that will measure 9.5
ohms...... or two 4.7 ohm in series will get you close if not right-on
depending on the individual and actual tolerances of the resistors.

Regarding the 90 ohm resistor you can try to find a standard 91 ohm or 100
ohm resistor that will be close or better yet, two 180 ohm resistors in
parallel..... or three 270 ohm resistors in parallel. If you have a large
sample of resistors to choose from you should be able to get very close.

There are lots of other combinations that will work but because of
manufactured tolerances you will need to go through a few off-the-shelf
values to get close to the actual resistance you need.

From what you described.... even though you did not mention what kind of
multi-meter it is, I would confidently wager (and win) that you are trying
to fix a Micronta #22-204 (Radio Shack) Analog Multimeter (or similar model)
....... if so, you need to realize that the analog mulitmeter tolerance is
not as tightly specified as most digital multimeters and therefore a slight
variance in these replacement resistors will not spell disaster.

The other common resistor failure is the 0.48 ohm resistor ...... I can
usually find an off the shelf 0.47 ohm resistor that will do the trick.

Note: When the 9.5 resistor opens up the RX1 range will be affected..... it
will look like it is working and will "zero" OK but just check a low ohm
resistor like 22 ohms or so and you will see that it is way off and reads
very high...... frequently check the RX1 range from time to time..... it
only takes one slip of the probe and the 9.5 ohm resistor is history.

I hope that all of this helps.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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snipped:

 

[Tweetldee]

I am in need of a 9.5 ohm and 90 ohm precision resistors for
Multi-meter repair. Does anyone know where I can find these
resistors? I not beyond series or paralleling resistors to get the
ohmic value.

Thanks.

You neglected to say what kind of precision these resistors need to have.
Assuming that you need 1% resistors, and since neither of these is a
standard 1% value, it's unlikely that you'll find them from a parts
supplier. Non-standard resistor values is the name of the game in
multimeters.
If the manufacturer can't or won't sell them to you, then your only
alternative is constructing your own, from other standard value resistors,
or by buying a lot of resistors close to your values and selecting those
that lie within the tolerance band of the needed value. The 1% values
surrounding the 90 ohm resistor are 88.7 and 90.9 ohms. Parts suppliers
like Mouser stock a wide range of resistor values, but they usually start
out at 10 ohms. For the 9.5 ohm resistor, your best bet is to calculate two
best fit parallel values and build your own.
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Time is what keeps everything from happening all at once.

 

[Stephan Goldstein]

You neglected to say what kind of precision these resistors need to have.
Assuming that you need 1% resistors, and since neither of these is a
standard 1% value, it's unlikely that you'll find them from a parts
supplier. Non-standard resistor values is the name of the game in
multimeters.
If the manufacturer can't or won't sell them to you, then your only
alternative is constructing your own, from other standard value resistors,
or by buying a lot of resistors close to your values and selecting those
that lie within the tolerance band of the needed value. The 1% values
surrounding the 90 ohm resistor are 88.7 and 90.9 ohms. Parts suppliers
like Mouser stock a wide range of resistor values, but they usually start
out at 10 ohms. For the 9.5 ohm resistor, your best bet is to calculate two
best fit parallel values and build your own.

Here's another trick you can use to make 90.0 ohms...


Get a 90.9 ohm 0.1% resistor - these are available from Mouser for a
very reasonable price. Parallel it with a 9.09k 1% resistor. The
resulting value will be nearly dead-on to 90.0 ohms.

You can use this general trick to make all sorts of special values.

Steve