TM Page 31
5.1.2
Suggested Installation for Inductive Head IH2-IH2/L with Power Pickup Loop in Split-Ring Assembly
a) Decide upon desired location for the strain gauges and split-ring assembly, preferably with a distance of 75mm or more
between the two. This is to prevent the inductive head magnetic field from inducing a voltage into the gauges or leadwires
and causing a "once per revolution" zero shift. The split-ring should also be positioned where any shaft displacement is at a
minimum, thus avoiding large variations in the air-gap between inductive head and the loop antenna on the split-ring
periphery. If the air-gap becomes too great a signal drop-out will occur. Finally, remember to leave space to mount the
inductive head - this location should be as far away as possible from metallic components or surfaces.
b) Install gauges, preferably using screened lead-out cabling.
Note: As the zero back-off at the analogue output of the telemetry system is limited to
±
20% of the full scale measuring
range, it may be a good plan to incorporate trimming resistor pads into the strain gauge installation to facilitate balancing of
the bridge output to zero. This will not be necessary if strain levels are high (i.e. several mV output).
c) Calculate value for Rg (and Rcal if used) and install resistor onto transmitter.
d) If not pre-installed, fit transmitter and counter-balance module into the TX.MTGS split-ring assembly and install ring onto
the shaft. If the split-ring assembly does not have an integral loop antenna, wind a single turn of insulated copper wire
(0.7mm diameter is supplied ) into the peripheral groove on the TX.MTGS ring and solder connect to the transmitter loop
connection pins (do not overheat).
e) Connect strain gauge leadwires to transmitter, also the strain gauge leadwire screen to the transmitter housing - this
ensures single point grounding for the complete transmitter assembly. When connecting strain gauge signal leads check
polarity to ensure that output voltage will read correctly (positive torque=positive V out) and not backwards. Fit transmitter
screening cover.
f) Position the inductive head IH2 using the supplied universal mounting bracket, as shown in figure 4.1, keeping it well
clear of metal components or surfaces. Set the airgap to 10-20mm and connect the head to the demodulator/decoder
module or unit TNC socket "PICKUP", using the supplied cable. Note that if the inductive head is located too closely to a
metallic mass, losses or de-tuning may reduce the transmitter supply voltage to less than the minimum acceptable level of
5.8VDC. It may be possible to compensate for this using the IH2 tuning adjuster, otherwise the head position will have to
be altered. Remember to lock the core with silicone rubber after making any adjustments.
g) Carry out checkout as per section 4.3.
Summary of Contents for TX31D/1/IFM
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