METER BASICS

Some people say they can't understand electricity because they can't see it. But we can't see into the gas tank of a car, either. We use a gas gauge to learn the fuel level. Likewise, meters take the mystery out of power systems. Here are the basics.

VOLTMETERS show electrical pressure, to verify when batteries are fully charged or are very discharged, but they are less precise at indicating mid-levels of charge.

AMP (short for amperes) METERS show current flowing at the present time. Amperes is a rate of flow, like gallons per minute. Turn on a light and 2 amps begin to flow. Turn on a second and the flow increases to 4 amps so long as both are on. We use a digital ammeter to show total amperes being used. If it reads higher than expected, we look for lights or appliances accidentally left on.

Ammeters can also be connected to show NET BATTERY AMPS - balance of power going in or out of a battery. If solar is charging 20 amps, and the TV is using 5 amps, the battery receives the difference, 15 amps. A net battery current meter shows +15 amps charge going to the battery. At night with just the TV on, this same meter shows negative 5 amps flow out from the battery.

AMP - HOURS is the total energy stored (or used) over a period of time, just like total gallons of gasoline available in the tank (or used on a trip). Amp-Hours is figured by the number of amps flowing multiplied by the number of hours they flow. A light using 2 amps, lit for 6 hours, uses 12 amp hours. If lit 30 minutes, it uses 1 amp hour.

A BATTERY NET AMP-HOUR METER starts at a full battery and counts amp hours passing into and out of the battery. It keeps track of the running total so you know how much charge is left in the battery. This is the closest thing to a fuel gauge yet invented for batteries. Batteries, like leaky gas tanks, loose a little power internally, where the meter can't measure it. To compensate, Battery Amp-Hour meters "fudge" the count lower 10 to 15% to match the actual battery condition. These meters must be carefully set up to match your battery. (See Tri-Metric meter)

METER SHUNTS are calibrated brass blocks that measure very large currents, up to 500 amperes, and send a small signal to a digital Ammeter or Amp-Hour meter. The signal can be sent on small wires, so the meter may be located some distance from the shunt, often in the living quarters for more convenient checking. All current going in or out of the battery passes through the shunt and is counted.

TRI-METRIC BATTERY METER
 NEW! Model 2025

IF YOU HAVE JUST ONE METER, MAKE THIS THE ONE!              

The Tri-Metric keeps a running total of power into or out of your battery and displays the present level of charge.

5" x 4-1/2"

The Meter head mounts anywhere in the house for easy checking. Small wires run from the meter to a shunt near the battery.

The Tri-Metric meter reads:

VOLTS: this feature only can monitor 2 battery banks, accurate to 1/10 volt. For 12, 24, or 48 volts.

AMPS or WATTS: display measures the rate of energy going in or out of your batteries so you can check your charging systems, and also to see how much energy each of your appliances use.

AMP-HOURS: Your battery state of charge in amp-hours.

% Full: display will give you a quick indication of battery state-of-charge.
Also shows advanced functions: Flashing alarm reminds that battery needs charging or needs equalizing. Shows days elapsed since last full charge; amp hours cycled since last full charge; total amp hours cycled since battery was new; lowest and highest voltage since reset. Visit www.bogartengineering.com for more details. 1 year warranty.

New Data logging feature records daily maximum battery voltage level, and minimum charging amps to check for proper charging levels for the last 5 days.

M-TRIMETRIC 2025 with all parts below 12, 24, or 48 volt:  $225 (shipping $12)
Backwoods Solar includes all parts needed to set up the meter: A 500 amp shunt  2/0 lug cable to connect battery to the shunt Terminal lug to attach your charge and load wires to the shunt, Surface wall mount box for the meter head 25 feet (or specify your length) of 4 conductor cable with 3 amp fuse for connecting meter to shunt and power.
M-TRIMET 2025 HEAD Meter head alone, no shunt or parts kit:  $180
M-SHUNT 100: 100 amp-100 mv: $29.00
M-SHUNT 500: 500 amp-50 mv: $29.00

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 DIGITAL PANEL METERS

DC VOLTMETER, digital  
Battery voltage reads to one decimal point. Reads accurately 11 - 65 volts. For 12, 24, or 48 volt power system. In surface mount box. 3" x 2" x 1"
 

M-DIG VOLT meter:  $45

DC DIGITAL AMMETER, with 100 or 500 amp shunt. Please specify which shunt! 

Digital ammeter shows small item power usage for lights and electronics, as well as high power battery charger and inverter current. Small wires connect meter to shunt so meter can mount remote if desired. With 100 amp shunt, meter reads from 0.1 to 99.9 amps. 500 amp shunt, meter reads 1 to 500 amps with no decimal place, for use with inverter DC circuit. You can't see such range or accuracy with analog pointer meters.

M-DIG AMP100 with 100 amp shunt...$68
M-DIG AMP500 with 500 amp shunt...$68

Minimum shipping $8 per whole order covers all items with no shipping listed

ANALOG (pointer) METERS

12V VOLTMETER, analog
Expanded scale for easier reading of normal battery range. Fits 2-1/8" round hole;
3 3/16" Wide x 2 7/16" Tall x 0.5" thick face plate (1.75" total depth)

M-AVOLT: Scale from 8-16 volts mounts in 2-1/8 " round hole:   $25

DC AMMETER, analog

Indicates amperes charging or DC usage. Fits 2-1/8 round hole. SPECIFY SCALE: 0- 5, 0-10, 0-15, 0-30, or 0-50 (no 0-25 as in picture);
3.5" Wide x 3.0" Tall x 5/8" thick face plate (2" total depth).

 

M-AMP: mounts in 2-1/8" round hole  $25

ROUND 60 AMP small analog meter, low cost, not extremely accurate. A good indicator that output from a battery charger is happening. Mounts in 2-1/8" round hole.

M-60AMP:  $15

GENERATOR MONITOR

Two meter unit reads AC volts & frequency (generator speed). No installation, just plugs into an AC outlet. Not accurate for most inverter waveforms.

M-GENTEST:  $75

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Minimum shipping $8 per whole order covers all items with no shipping listed

PORTABLE DIGITAL TEST METER

VOLTS shows 2 decimal places up to 20 volts DC, and one decimal place up to 200 volts DC. This is important for checking battery condition, with tiny variations between some cells.

AMPS reads up to 10 to 20 amperes DC(depending on model currently in stock), enough to test the current of a solar module or many DC appliances. 

OHMS and milliamperes scales, audible continuity beep, diode test etc.

This Tenma brand meter costs more than hobby types, and is very reliable- no breakdowns or returns. 1 year warranty. 3" x 6". We send a brochure about using a test meter with each order. Or ask for just the Backwoods test meter instructions for study, free. (Picture may differ from meter in stock)

M-DMM Tenma Digital Test Meter:  $50

AC WATT HOUR METER 

Compares Power Usage of Appliances

Plug this meter into 120 volt AC power and plug appliance into the meter. It registers how much power the appliance is using, and keeps total of kilowatt hours used since start of test. You know exactly how much energy a freezer uses each day, or any other appliance. Measures power draw up to 1875 watts. Easy to switch among appliances and loan to friends for appliance comparisons. Shows voltage, frequency, and power factor of power being used too.

M-KILL-A-WATT  :  $40

Minimum shipping $8 per whole order covers all items with no shipping listed

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