Need advice on amp settings

[FJ and G]

On my new multimeter you can dial up 4 different amp settings (shown a-c; the numbers are main categories).

1. uA/A=

a. AC 0.4/4 mA
b. AC 4/10A

2. mA/A=

c. AC 40/400 mA
d. AC 4/10 A

I don't want to fry my circuits with amperage on the toy train layout that is too high for the dialed value.

Thanks!

Dave V

[Big_Boy_4005]

Dave, b and d appear to be the same value. Is d supposed to be 40/100 A? I would think that b, the 4/10 A should handle your model railroad best.

[FJ and G]

Thanks, Elliot,

Don't know.

Now you see why electronics can be intimidating. If instructions were more clear, more people, IMO would enjoy this part of the hobby!

[Anonymous]

Does your meter have a separate plug for the 4/10A range? If so, b and d are probably the same. This is done so the multimeter switch does not have to handle high currents.

Daniel Lang

[Anonymous]

The max amperage your meter can handle is 10 amps. So if your running 18 volts and 180 watts the max ampreage output is 10 amps (this for a typical lionel powerhouse transformer). If your voltages and watts are different divide watts by volts to get the max amperage180/18=10. The amperage all depends on how much power is being drawn used. If your engine is not running you will show very little 0 amperage. If your engine is running slowly then you will see maybey 1to 3 amps. If you are running an engine at high speed the amperage will be higher maybe 5 or more. It all depends on how much current you are drawing using. Multimeters are not usually used to measure amperage the max is 20A. For higher amperages you should use a clamp meter up 1000A. I don't think you should have a problem measuring the amperage on your track with your meter. Do not exceed the max 10 amp rating of your multitester because it will be damaged.

[webenda]

FJ and G

The Radio Shack 22-811 is an auto-ranging meter. When the switch is in the 0.4/4 mA range the input is across a 4 mA shunt. If the current is below .4 mA
the meter ranges down to read 0.4 mA full scale. If the red test lead is moved to the 10 Amp input, the input is across a 10 Amp shunt. It does not matter
if the switch is in the 0.4/4 mA range or 40/400 mA range. The input is still across the 10 Amp shunt. If the input current is below 4 amps, the meter auto-
ranges to read 4 amps full scale. If the input is above 4 amps, the meter autoranges to read 40 amps full scale. Since the shunt is only rated at 10 amps, it cannot be used for currents above 10 amps. Using it above 10 amps may heat it enough to change its calibration.

In another post, macaste said that he had a Fluke multimeter that was more precise than less expensive brands. He did not say what model he has.

Let's compare a Fluke Model 77 to your RS 22-811.

Fluke Model 77
10 amps AC .. ± 2.5% of Reading, ± 2 in Last Digit
or 10 amps ±(0.25 + 0.02) = ±0.27 amps.

RS 22-811
10 amps AC ±1.5% of Reading, ± 5 in Last Digit
or 10 amps ±(0.15 +0.05) = ±0.20 amps.

Macaste also said that expensive meters come with a certificate of calibration. The certificates do not say so, but the calibration expires in one
year. That really is not important to us, because we do not have to prove that our measurements are accurate. However, I have found the Radio Shack meters to be accurate and to hold that accuracy for years. I have three Radio Shack meters that I calibrated when they were new to verify that they were in specification. All three were. One of them has had yearly calibration four times. It is still with-in specification.

I hope this helps.

Wayne

[Anonymous]

I have a model 87 III. The max amperage I can measure is 20A but only for 30 secs. It is good but so are a lot of other multimeters.