FUTEK IPM500 (D500) Digital Display - Manual (Page 33)

33
RTD & RESISTANCE CONNECTION
With the appropriate jumper settings, RTD
and resistance measurements allow 2, 3 or 4-
wire RTD hookup to the J5 connector, as
illustrated. The meter applies an excitation
current, which it monitors to make ratiometric
corrections for excitation supply variations.
In 2-wire hookup,
the meter senses the
voltage drop across the load and both lead
wires. The effect of the lead wires can be
measured and subtracted by shorting out the
load during meter setup. The short should be
as close as possible to the load. Ambient
temperature changes will still cause some
error in the readings -- the higher the lead
resistance, the greater the error.
Under the .
Short .
menu selection, the load is
shorted out, the key is pushed, a value
proportional to lead resistance is displayed,
and that value is automatically stored in the
meter. After this step, the RTD type or resist-
ance range need to be selected.
In 3-wire hookup, the meter automatically compensates for lead resistance by measuring the
voltage drop in one current-carrying lead and assuming that the voltage drop in the other
current-carrying lead is the same.
In 4-wire hookup, no compensation for lead resistance is necessary. The step of shorting out
the RTD during meter setup is not necessary with either 3 or 4-wire hookup.