5. CHANGING SETTINGS
IM 2493WVP-1
14
A unit with 1mA output can be configured by the user to range from 0 to 1 mA or
from –1 to 1 mA. This setting is referred to as CEN (short for ‘center’) on the
front panel display. If the unit is set to 0-1 mA it is guaranteed never to have an
output below 0 mA, regardless of the input. If the unit is set to be a –1 to 1 mA
unit then the output will be negative DC current whenever the input falls below
the LO setting. If the unit is set to be a –1 to 1 mA unit, the LO value then
indicates the midpoint of the range, not the lowest point. Another way to phrase
it would be - the LO value always indicates where the output will be 0 mA.
For example:
A 1 phase 2 wire 120Volt 5 Amp wattmeter has a LO setting of 100 watts and a
HI setting of 400 watts. If it is set to be a 0-1 mA unit, then at 100 watts or less
the output will be 0 mA. If it is configured to be a
±
1mA unit and still has a LO
setting of 100 watts, then at 100 watts the output will be 0 mA, but at 70 watts the
output will be –0.1 mA and at –200 watts the output is –1.0 mA.
In this same example, while set as a
±
1 mA unit, the LO could not be set any
lower than –250, because the span between HI and LO cannot extend lower than
the Minimum LO, which in this case is -900. (See tables below for a complete list
of limits) That is:
LO – (HI – LO) must not go below the LO limit
È
-250 – (400 – -250) = -900.
For 4-20 mA units there is no CEN option for changing the range of the output.
Changing the Analog Output Settings
When you reach the ‘out1’ (Watts) display, press Set and the value of CEN1 will
be displayed if the unit has 0-1 mA output. A 4-20 mA unit will display the value
of HI1. If you have a 4-20 mA unit disregard the instructions for CEN1.
For 0-1 mA units - Pressing Set again will cause the center display to begin
blinking. Pressing Inc will switch the setting from “0-1” (0-1mA) to “–1-1” (
±
1mA)
and back again. Press Set to save the displayed value and move you to the HI
setting.
