26
3.2.7
SENTINEL®
S
CREENS
The SENTINEL feature allows the Model T80 transmitter to provide Pre-pHault
diagnostic information about the accuracy of a pH, ORP or pIon measurement. The
SENTINEL displays a filled triangular gauge that decreases proportionally to the
degradation of the reference electrode. A filled gauge indicates a properly
functioning measurement while the emptying gauge indicates the remaining life of
the electrode. This Pre-pHault diagnostic alerts the user to potential problems and
provides a visual indicator of the sensor’s remaining life before the measurement
actually fails.
The Model T80 transmitter only displays the SENTINEL functions when a Model S80
SENTINEL sensor is connected. The Model S80 SENTINEL sensor uses Diagnostic
electrodes designated by Part#’s 20053XX, these electrodes use a triaxial connector with a, PV connection (pH,
ORP, Ion), Reference connection and Diagnostic connection.
On a dual channel instrument an asterisk *, will be displayed in the sensor name block, SENSOR 2 *. The
SENTINEL function will only be visible in the Single Screen mode, not in the Dual Screen mode. Toggle the BACK
Key from Dual → Sensor 1 → Sensor 2 to see the SENTINEL function.
Configure SENTINEL Function
The SENTINEL function is located in the Configure Sensor menu:
CONFIG → SENSOR → SENSOR 1 or 2 →MORE → SNTL
There are three values displayed:
V
o
= SENTINEL Voltage offset, The diagnostic voltage of a new electrode
V
e
= SENTINEL expiration Voltage, V
o
+ Range
RANGE = The shift in the diagnostic voltage required to trigger diagnostic fault.
The default values of V
o
= 0.0 mV and the Range = 60 mV are good for most
situations. The starting diagnostic voltage is typically near 0 mV on a new electrode
and if the readings have drifted 60 mV apart (a full pH unit) then electrode service is
required.
