Insert the lead wire into the modular connector at the rear of the meter. Then insert the dummy gage resistor on the small connector into the lead connector so that the resistor is between the pins not containing the black (ground) wire. Install an alkaline 9V battery in the battery compartment. Do not use a NiCd rechargeable type unless it is a full 9V type and not a 7.2 V type. Even then, the alkalines will last longer.
The balance trimmer normally only needs adjustment after initial system setup, and will not require readjustment between measurement sessions.
Place the right slide switch to the rear balance/track position and turn the unit on with the left slide switch. A reading will appear on the display. If the reading is 1 or -1, the bridge balance is out of range and must be adjusted. There are 2 small holes on the right edge of the meter that are the access to the 15 turn trimmer balance and calibration adjustments. Use a small straight shank 3/32" screwdriver like an Xcelite R3322 to turn the trimmer screw. Sometimes it helps to shine a light into the holes to see the screw slot alignment before trying to engage it with the screwdriver. Adjust the rear trimmer to the right (clockwise) if the reading is -1, or the other way if it is at 1. Keep turning until a transition is seen, then adjust slowly to a reading close to 0. If the screw makes a clicking sound and keeps turning, it is at the limit. If no balance can be obtained, it means there is a bad connection in the lead wire. Sometimes the unit may appear to balance near the limit of the adjustment when the gage is not connected. This can be detected by pulling out the lead wire connector and seeing if the reading changes. If the meter does not read 1 or -1 when the leads are pulled, that indicates a false balance. This balance reading should be between 500 and -500 for best dynamic range.
The balance reading will drift with temperature and vary with lead length or when switching to a different gage. The reading represents the feedback compensation used to keep the meter zeroed when in the peak hold mode. The meter can be used in this mode to measure static strain differences by subtracting the final reading under stress from the initial prestressed strain reading.
It should be stressed that it is unecessary to worry about setting the balance to exactly 000. The balance need only be in the -500 to +500 range to operate well in the peak hold mode. The meter is self baseline correcting in that mode - any drift in balance is self corrected. That is why the balance need only be set initially.
After the unit has been warmed up a couple minutes, and the balance has been adjusted, slide the right switch down to the peak hold position, then push the left push button, the reset button. The meter should read 000 or very close to it. Next push the test/calibrate button on the right. The meter should display a reading near 777. Hit the reset, wait a few seconds and repeat the test. Keep note of the readings. Most of the readings should be very close to each other with a few reading a bit lower. The low readings are due to contact bounce effects. Some switches are more susceptible to this than others. The switch used in the meter has been selected for good performance, but if more than half the readings are seen to be low, the switch should be replaced (contact Fabrique Scientific).
When one of the higher base readings have been obtained, adjust the calibration trimmer for a reading of 777 plus or minus a few. This will set the calibration of the unit to within a percent or so (see the section on gain and calibration details) to read directly in micro strain (parts per million, or micro inches per inch, etc.). The calibration is stable and will not usually need to be readjusted. The reading should droop very slowly and will normally hold for half a minute or so before dropping a division depending on the temperature.
The calibration can also be tested in the track/balance mode. Note the reading, push and hold the calibrate button and note the reading when it settles. The difference in the readings should be near 777. There will be some discrepancy between the readings taken in peak hold vs. track/balance mode. The reading in peak hold mode will generally be 1.5% or so higher. The small difference can be compensated for by calibrating in the appropriate mode.
The flat unshielded telephone type lead wires may be used, but they are subject to high frequency noise pickup. The meter will filter some noise out at the second stage, but if the meter is equipped with the optional oscilloscope output, the scope trace will be noisy. A shielded cable will prevent the noise pickup and may reduce variability in the meter readings, although the unshielded cable has been used to give readings good to about 2% standard deviation. Short lead wires will also reduce noise pickup.
Consult the notes on gage installation, and wire the leads to the gage. Insert the lead wire and set the unit to balance mode and turn it on. Adjust the balance if necessary, as in the above section, to read around 000 +- 500 or so. Switch to peak hold, reset, and push the test button to verify the calibration reading is near 777. Switch back to balance/track mode and try bend the barrel of your gun. Often you will be able to observe changes in the reading due to your hand stress of the barrel. To operate, just put in peak hold mode, reset, shoot and record the reading. Don't forget to hit reset again before each shot.
The connector configuration numbered from 1 to 4 from left to right looking down from the top with the meter facing you in normal operational configuration so the display can be read is as follows:
1: Ground - connected to the gun barrel at the far end
2 and 3: connected together at the far end to one lead of the gage
4: connected at the far end to the other lead of the gage
No balance can be achieved -
Check for 350 ohms between the red and yellow wires on the lead wire with the gage attached. Could be faulty modular connector on lead wire or bad connection to gage.
Track mode reading fluctuates -
Probably bad connection on lead wire modular connector - replace connector or lead wire.
Erratic high readings obtained from some shots -
Check if there is a source of electrical interference like nearby transmitters or walkie talkies. Due to the sensitive nature of the electronics, the lead wires can pick up interference from high electrical fields. This can also occur from bad solder joints on the gage.
Sometimes anomalous high readings are experienced with hot loads due to barrel vibrations that occur at bullet exit that sometimes exceed the peak strain due to the chamber pressure.
Reading does not hold steady -
This could happen if dew conditions exist inside the meter. Let
the meter warm up to ambient temperature before use. If the reading
changes if the meter is touched or moved, this may indicate a
bad connection on the internal shielding. The meter droop rate
is sensitive to the leakage resistance of the reset switch and
may require custom selection of that component.