Current reading

[fixit7]

I have an Excel XL830 meter. When testing current, the scale is a bit confusing.

When set to the 2 ma scale, my reading showed .04 for the load used by the clock.

It uses lcds to display time,date,temp,and month day year.

Do I move my decimal to the right one place?

.04 or .4 ma ?

I need the value to calculate the run time when using 2 AA batteries.

I will use a capacity of 2200 Mah.

 

[Pommie]

Without knowing the meter it's hard to say but I would guess 40mA as that is 0.04A. However, that makes no sense on a 2mA scale. What does it read on a 1A scale?

Mike.

 

[Nigel Goodwin]

Without knowing the meter it's hard to say but I would guess 40mA as that is 0.04A. However, that makes no sense on a 2mA scale. What does it read on a 1A scale?

Mike.

Seems fairly obviously 40uA - a 2mA range will actually be 1.999mA, it would be a VERY strange meter if it did differently.

And 40uA sounds about right for an LCD clock.

 

[audioguru]

Instuctions for the meter are in Google:
1) Black probe in the COM jack.
2) Red probe in the V/Ohms/mA jack.
3) Set meter on the 20mA, 2mA or 200uA range.
4) Connect probes in series with battery and circuit. Hey, you cannot connect its probes in series with its own battery!

0.04mA is correct for an LCD clock. Then a 700mAh 9V battery lasts for 730 days.
If the reading is much too low then the 200mA fuse is blown or the battery is weak and the meter shows Low Batt.
A cheap Sooper Heavy Dooty Chinese 9V battery will last for about 1 day.
A Name Brand alkaline Western 9V battery will last for 730 days.

 

[fixit7]

Instuctions for the meter are in Google:
1) Black probe in the COM jack.
2) Red probe in the V/Ohms/mA jack.
3) Set meter on the 20mA, 2mA or 200uA range.
4) Connect probes in series with battery and circuit. Hey, you cannot connect its probes in series with its own battery!

0.04mA is correct for an LCD clock. Then a 700mAh 9V battery lasts for 730 days.
If the reading is much too low then the 200mA fuse is blown or the battery is weak and the meter shows Low Batt.
A cheap Sooper Heavy Dooty Chinese 9V battery will last for about 1 day.
A Name Brand alkaline Western 9V battery will last for 730 days.

You do not get the gold star today.

As my post states, I am using 2 AA batteries not a 9V battery.

2200 mah / .04
------------------
24 hrs
= 2291 days = 6 yrs.

Does that sound reasonable? I am thinking that the current is .4 milliamps.

I read somewhere where those batteries should last around 2 years.

 

[Nigel Goodwin]

I am thinking that the current is .4 milliamps.

Why?, when it clearly displays 0.04mA (40uA), which as we've both said looks pretty spot on for an LCD clock.

 

[fixit7]

You are right. I checked a part with a listed current of under 18 ma.
It read 14.4.

Looks like my batteries will last around 6 years.

 

[KeepItSimpleStupid]

Remember that the simple meters insert a resistor, thus the voltage can also change. The drop is normally less than a diode drop of 0.7 V becaue diodes are used for protection. So, lets say 20 mV and 20 mA is a design goa, so a 1 ohm resistor is used. 20 mV being a displayed value/ Insertion at full scale will drop 20 mV. Check your meter specs.

ASIDE: I had a Harbor Freight $5.00 meter read 112 VAC on a telephone circuit with DSL to ground. I forget if it was tip to ground or ring to ground. One read 2.5 VAC and the other 112 VAC.

The meter read 120 VAC on a normal AC line. What's wrong? I put a DSO150 scope on it and found a 500 kHz signal on it, so I suppose the meter does not have an RFI filter on it.

 

[audioguru]

The cheapo (7 bucks, free shipping from China on ebay) Chinese meter does not spec its "burden" voltage drop when measuring current.
2200mAh is fairly low for modern Western AA alkaline batteries. Energizer or Duracell AA alkaline cells would last their entire 10 years storage guarantee powering this clock.

 

[fixit7]

I know my meter is not top of the line.

When it goes belly up, I will use this resource.

Index of reviewed multimeters below $150 table

lygte-info.dk

I MAY go with the UNI-T UT191T.

 

[Nigel Goodwin]

Energizer or Duracell AA alkaline cells would last their entire 10 years storage guarantee powering this clock.

Duracell would probably leak all over it before the ten years are up!.

 

[audioguru]

I forgot that I have never purchased Duracell Alkaline cells because they leak. Duracell and Energizer Japanese Ni-MH cells are excellent.

 

[Mickster]

I've had some Duracell batteries leak before the damn packet is even opened!

 

[fixit7]

Duracell would probably leak all over it before the ten years are up!.

I am using Radio Shack's fine batteries.

I could put some backing soda around batteries to neutralize any acid leak.

 

[Nigel Goodwin]

I've had some Duracell batteries leak before the damn packet is even opened!

Historically Duracell batteries NEVER leaked, and I've seen a LOT of leaking batteries over the years - however, a good many years ago now they obviously changed their construction because they became (and still remain) one of the biggest culprits for battery leakage.

 

[rjenkinsgb]

they obviously changed their construction because they became (and still remain) one of the biggest culprits for battery leakage

Agreed! These were memory backup in a machine tool; a set of batteries often last 5 - 10 years.

This set was still within the "use by" date, if I remember right:

View media item 34