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MPX15 Addendum
Wiring Details
Wiring details for the Parallel Twin mode have been changed since earlier versions of this manual were issued.
New versions of figure 2-6, on pages 2-9 (for new PA5 frames) and C-3 (for old style PA5 frames) are shown
in this manual. Wiring detail recommendations have also changed since white papers were issued in 2001 and
2002 concerning striping problems with the Parallel Twin mode.
Procedure For Checking Probe Configuration Wiring
You can easily check to see if you have the multiplex configurations wired and orientated correctly. Set the
system up for taking your first measurement, with the frame and resistance meter in front of you. Press Enable
Log and you will see a reading made with the first measurement pair, A1 / M1 if using a Twin array. Unplug
the jumper lead for A1 and you should see an “HCR Open Cct” message (current probe). Reinsert that jumper
lead and next unplug the jumper lead for M1 and you should see “Over-range” message (potential probe) or a
reading that wanders up and down. Reinsert the jumper lead for M1. Next log a complete cycle and delete just
the last reading using the DEL key so you are now measuring A2 and M2 (for 2 multiplex cycles). Again
repeat the process described above but this time apply it to A2 and M2. If there are more than two multiplex
cycles follow the same procedure and bear in mind you will be stepping back from the end of the cycle.
PA5 Probes
Probes for the PA5 system are now provided with a neoprene sleeve and rubber grommet to provide extra
protection against moisture.
A 25mm length of neoprene tubing is provided for the top of each probe. The tube internal diameter is slightly
less than the diameter of the plastic at the base of the handwheel so should form a tight seal at this point. At the
other end it will compress against the beam or wing, enclosing the nylon and steel washers which have a
diameter less than the internal diameter of the neoprene.
A rubber grommet is provided for the bottom of each probe. This slides down the probe until it pushes against
the steel nut at the base of the probe. It will form a tight seal with the probe since its internal diameter is
slightly less than that of the probe. It’s diameter is about 25mm and thickness 8mm. When a white mud cap is
pushed into place this presses against the grommet forming a seal.
Care and Maintainance
It is very important to look after and maintain the PA5 frame system to minimise measurement errors that can
occur, especially in wet weather conditions. These errors are most noticable when making Parallel Twin
measurements and take the form of striping in the data. This is discussed later on in the addendum. Please
observe the following points :
•
Always keep the system as clean and tidy as practicable since moisture and mud will inevitably cause
current leakage problems and result in measurement errors. Dry equipment out thoroughly after use
and do not store in damp conditions (in much the same way you should do if you want to keep a
mountain bike in good condition).
•
If soil conditions are very salty then consider washing down and drying equipment immediately after
use. Soils heavy with salts may cause more leakage problems than “normal” soils, especially if caked
on.
