User Guide

12
ORP CALIBRATION (HI8615 & HI8615L)
Initial preparation:
Disconnect the +ve supply cable from the
"+VE LOOP" terminal and connect a 20 mA
f.s. ammeter between the +ve cable and the
"+VE LOOP" terminal. With HI 8615L the
instrument display can be used during cali-
bration without the need to connect the am-
meter. In this case the values are directly
expressed in mV units.
Pour a small quantity of
HI7020 ORP solution into a
beaker.
Procedure:
• Connect the shorting BNC
connector to the ORP trans-
mitter.
• Adjust the OFFSET ADJUSTMENT trim-
mer on the module for a display of 12 mA
on the ammeter or 0 mV on the instru-
ment display (HI 8615L only). This sets
the zero point for the transmitter.
• Connect the ORP electrode to the trans-
mitter and immerse the tip of the elec-
trode into a beaker of HI7020 ORP cali-
bration solution, and check that the am-
meter reading lies between 13.6 and
14.2 mA or the instrument reading is be-
tween 200 and 275 mV at 25°C (HI8615L).
H
I
7
0
2
0
INPUT
-VE LO
O
P
+VE LO
O
P
mA
SLOPE ADJUSTMENT
OFFSET ADJUSTMENT
mA
HI 7020
INPUT
-VE LO
O
P
+VE LO
O
P