For medium and larger systems most people use the 500A/50mV shunt. There are two things to consider when deciding which to use:

1. If you will be measuring current with the meter that is greater than 70 Amps (charging or discharging) then the 100A/100mV shunt is too small (it will overheat), and you should use the 500A/50mV shunt. For example, a 12 V battery system with an inverter over 800 watts could exceed this, and the 500A/50mV shunt should be used. The maximum current in Amps in this case is 800 divided by 12, which is 66 Amps.

2. If you will be measuring current with the meter that is less than 70 Amps, then you may use either a 500A/50mV shunt or 100A/100mV shunt. But the 100A/100mV shunt will allow you to see on the meter currents as low as 0.01 amps, whereas with the 500A/50mV shunt you will see currents only down to 0.1 amps. So with smaller systems you will be able to more accurately measure very low currents with this shunt.

More detailed information on shunts is available on this web site, titled "Shunt Info" under "Support", "Application Notes" then "TriMetric|PentaMetric."

Call for technical help. We do not like this one--and we are trying to determine the cause!  This has happened a few times, and often seems associated with turning power off and on to the meter--for example after changing batteries. Probably a warranty repair.

Troubleshooting:

The causes of this are numerous, which come under three broad categories, running from what we find “most common” to “least common.”
 

1. The meter does not read correctly because of a problem in battery or charger wiring connecting to the  shunt, or  from the meter to shunt, or possibly wrong shunt.

2. The meter is actually reading correctly, but the person reading it  is making a wrong interpretation of what it means.

3. The meter does not read correctly because it has an internal problem:

First check the four or five wires  coming from  terminal block on the TriMetric to shunt and battery to insure it is properly connected using the wiring diagram in the TM2025 Installation instructions.  (Most importantly the G2 and Sig wires from meter and shunt)   Using a sufficiently small screwdriver for the terminal block, be sure all screws are reasonably tight on the wires.  Also check connections at the shunt Kelvin screws.

A1: Did the meter never  read correctly from the time it was  first installed--or was some recent change made to batteries or connections, and since then it does not read correctly..

A2: f the “amps” used to read  fine, but now do not, even though no change has been made to battery wiring  or meter since it worked.

Six most common symptoms: If you have an “amps” problem that is in none of these categories, please call us for technical help  (and so we can update this troubleshooting section.)
 

B1: The meter always reads 0.00 amps, even when any load or charging source is turned on.

B2: The meter reads a (non zero)  “offset” value of amps greater than 0.1 amps, but usually less than 10.0 Amps, even when all loads or charging sources are off. When a load is turned on the amps value changes by the amount that you would expect that load to draw.  Likewise charging sources make amps more positive iby the amount you would expect them to be supplying. For example, there could be an offset value of -1.5 amps with no loads or sources, but when turning on a 12W compact florescent lamp that requires 1.3 amps makes the meter now show -2.8 amps when on.

B3. Meter reads large offset value: may be less, but often more than 50 amps, which may drift  slowly with time even when  you know loads or charging sources are not changing..

B4: The meter may read a positive value of amps  when charging, and loads register negative values as they are supposed to.  But they do not appear to be the correct magnitude.  Possibly do not agree with another meter that measures “solar input amps” for example.

B5 The meter reads some or all “load” values OK, but it doesn’t measure one or more charging sources, such as solar or wind.or external charger. It may be true for just one charging source.  Check each one.  Do they all behave the same? or is just one of them not responding? Also it could be one load that does not seem to register.

B6: Values of “amps” seem correct, but “charging sources show as negative values and loads show as positive values.

Fixing the problem:

If symptom B1 or B6: ,

    Check that each wire is connected correctly from meter to shunt and battery.  Particularly, check the “G2” and the “Sig” wires coming from the meter terminal block to the shunt “Kelvin” screws. Make a note of which end of the shunt is connected to the battery minus connection.   Make certain that the wire from “G2” goes to the little screw FARTHEST from the minus connection, and that the “Sig” wire goes to the screw CLOSEST to the minus connection.  Symptom B1 would result if both are connected to the same screw,. Symptom B6 would result  if they were connected to different screws, but backwards..

If symptom B1 or B5:

    Look at “figure 1” in  the TM2025 “INSTALLER” instructions.  Read the text below the two drawings, and check that your shunt, as installed,  follows the guidelines.  Be sure that NO CABLE or WIRE except ONE END OF THE SHUNT, goes to the negative terminal (or terminals  of batteries are in parallel) of the battery.  This means no grounds, solar connections, extra temporary chargers.  Anything of this kind (or others) should go to the OTHER END of the shunt that is not connected to the negative post(s) of the battery, or the amps will not get measured from/to that device.

If symptom B3:

    Check the two wires G2 and Sig  from the terminal block of the TriMetric.  Look for a broken, loose, or disconnected wire.  Check that  the screws of these two are reasonably tight at the meter, and check that the connections are good at the two Kelvin connections (small screws) on the shunt. If the meter used to be OK , and now is not, please note that mice have often been known to chew and break these wires somewhere between meter and shunt.

If symptom B2:
 

Possible Cause 1: Possibly an overlooked load is really present on the battery.  For example: inverters that are “on”  with no loads require at least a little power--some less expensive ones muchmore. Even when “off” usually require  a little.  Carbon monoxide detectors present or other light loads? Turning of a main breaker to the battery, with the TriMetric still powered to the battery can eliminate this cause. Even the TriMetric, when the display is lighted to read “amps” will take about 0.03 amps, which can be read with  the “100A/100mV shunt.

Possible Cause 2: Check that the G1 and G2 wires from the meter join together only right at the Kelvin screw on  the shunt.  They should NOT be joined together close to the shunt, then using a single wire to go the last few inches, for example.  Also, this can  be caused by any short in the wires that would cause the G1 and G2  wires to connect together on its way except right at the screw.

If symptom B4:

Possible Cause 2If you see a difference between what a solar charge controller comes in, and what the TriMetric says, remember that the charge controller shows ONLY what comes in from the sun, and the TriMetric shows you what comes in minus whatever loads might be drawing. In this case the controller will always show a positive value, and the TriMetric could show a value LESS than this, or NEGATIVE depending on loads. So it may showing you the correct value.

Possible Cause 2if the numbers are high or low by a factor of ten., either 10 times higher or lower than expected. You have the wrong shunt-- this would usually be indicated  Set the TriMetric for the correct shunt. Program P10 or change the shunt,

Further analysis for people with some technical skill:
    Further troubleshooting that will really nail down the problem can be tried if you have a multimeter that reads “millivolts”.  Such meters often read as low as 0.1 millivolt.  Follow this procedure:

1. Turn on a  steady load that you would expect should register at least 10 amps or so on the TriMetric. If the load is too small you might not be able to readily see the numbers below. However if  you are using the 100A/100mV shunt you could use a smaller load of an amp or two.

2. Put the multimeter to the “millivolts” scale and measure across the “Kelvin” terminals of the shunt (near the battery)  to see how many millivolts are present between the two Kelvin screws.  If you are using the most common 500A/50mV shunt and you read 1.0 millivolts that would represent 10 amps of current flow through the shunt. (0.1 millivolt per amp)  If you have a 100A/100mV shunt that would represent 1.0 amps.  Record the reading of millivolts and amps..

3. Check TriMetric “amps” and see if the number of amps corresponds to what you measured. As stated, with the 500A/50mV shunt each 1.0 millivolt represents 10 amps.

4. If the meter is reads the value correctly, the TriMetric  is OK.  If not, bring multimeter to the TriMetric, gain access to the terminal block on the back and measure the millivolts between the “G2” and “Sig” terminals.

a. If you now measure the same number of millivolts as at the shunt, but the meter “amps” reading still does not correspond, then the meter must be bad.

b.  If the reading is different from what you measured at the shunt:

Then most likely the wiring has a problem. Either there is a short to the G2 or Sig wire on the way to the shunt.  Though unlikely,   it COULD  be a TriMetric problem.  To resolve this question: carefully disconnect the G2 and Sig wires that go to the shunt  from the terminal block on the circuit board--be sure they don’t slip and touch something on  the circuit board, which could damage it  Then measure the millivolts between the two wires while they are disconnected.  If the value is now the SAME as what you read at the shunt, then the TriMetric needs repair. If it is NOT the same as what you read at the shunt, then it is the wires to the shunt that probably are shorted to something.  In this case, go back to the shunt again and measure the millivolts at the shunt to confirm that the value hasn’t changed.