GENERAL INFORMATION
MOUNTING POSITION AND LOCATION
PRELIMINARY OPERATIONAL CHECK
MOUNTING POSITION AND LOCATION
Unit may be mounted in any position or orientation. Refer to
Figures 1 and 2.
Figure 2 – Vertical Mounting
3
PRINCIPLE OF OPERATION
The Trident Model 91S/92S operates on a two crystal
pulsed or “transmit-receive” principle which applies a high
frequency electronic burst to the transmit crystal. The signal
is then converted into ultrasonic sound energy and transmit-
ted across the sensing gap toward the receive crystal. When
air is in the gap, the high frequency sound energy will be
attenuated, thereby not allowing the energy to be received.
When there is liquid in the gap, the sound energy will propa-
gate across the gap and the relay control or current shift
output will indicate such a reception of the signal.
Self testing is accomplished without any additional crystals
and a minimum of additional circuitry. The electronics detec-
tion circuit looks for low amplitude signals that pass between
PRINCIPLE OF OPERATION cont.
the crystals through the frame of the sensor. This allows the
entire sensor, including the bond between the crystals and
the sensor face, to be tested along with the electronics.
UNPACKING/SPECIAL HANDLING CONSIDERATIONS
Before unpacking the unit, please familiarize yourself with
the procedures and cautions regarding the handling of
Electrostatic Discharge (ESD) sensitive equipment.
MOUNTING POSITION AND LOCATION cont.
When installed in a nozzle or pipe, the transducer gap must
extend into the tank beyond the inside tank wall. Refer to
Figure 3.
Figure 3 – Horizontal Mounting in Nozzle
All wiring, conduit and electrical fittings must conform to
local electrical codes for the location selected.
Figure 1
Horizontal Mounting
(91S only)
Direction of
Level Movement
1. See appropriate wiring for Four-Wire/Two-Wire and sin-
gle point/dual point models (pages 4–10) and wire unit.
2. Fill a suitable container with water.
3. Place transducer gap in the liquid.
NOTE: THE AMPLIFIER BOARD AND POWER SUPPLY
BOARD WILL BE DISCUSSED THROUGHOUT THIS MAN-
UAL. THE POWER SUPPLY BOARD IS SHOWN IN FIG-
URES 4, 5, 6, AND 7, DEPENDING ON THE VERSION. THE
AMPLIFIER BOARD IS SHOWN IN FIGURES 9, 11, AND 12.
Single point (91S) models
Relay Versions: Once the liquid fills the gap, there
should be an audible click as the relay changes state.
Also, the red LED marked LED1 (WET) on the amplifier
board will illuminate. Depending on how the unit is con-
figured, the red LED marked DS1 on the power supply
board may also illuminate. For the purposes of this pre-
liminary check, only the LEDs on the amplifier board are
pertinent.
Current Shift Versions: Once the liquid fills the gap, the
current output value should change from 8 mA to 16 mA,
and LED1 (WET) on the amplifier board will illuminate.
Dual point (92S) models
Relay Versions: Place the lower transducer gap in the
liquid. There will be an audible click as the relay changes
state. The red LED marked LED1 (WET) on the bottom
amplifier board will illuminate. Continue to immerse the
transducer until the top gap is filled with liquid. Once
Dual point (92S) models cont.
again, there will be an audible click as the relay changes
state and the red LED marked LED1 (WET) on the top
board will illuminate.
Current Shift Versions: Once liquid fills the lower gap,
the current output value should change from 8 mA to 16
mA, and the red LED marked LED1 (WET) on the bottom
amplifier board will illuminate. Continue to immerse the
transducer until the top gap is filled with liquid. Once
again, the current output value will change from 8 mA to
16 mA and the red LED marked LED1 (WET) on the top
amplifier board will illuminate.
4. Remove transducer from the liquid. The control output
must deactuate or current shift value return to 8 mA* and
the green LED marked LED2 (DRY) will illuminate. In case
of malfunction consult the Troubleshooting section on
page 15.
MANUAL SELF-TEST
Wet Self Test: With power applied to the instrument and no
liquid in the sensor gap, press switch S2 marked WET
TEST on the amplifier board. Red LED1 (WET) on the
amplifier and DS1 power supply board will illuminate, and
green LED marked LED2 (DRY) on the amplifier board will
extinguish.
Manual Self Test: Press switch S1 marked MALF TEST on
the amplifier board. With P2 jumper on the amplifier board
in (HIGH) position both LEDs on the amplifier board will illu-
minate. With P2 jumper in (LOW) position, both LEDs will
extinguish. Output current should be 19 mA or 5 mA
respectively.*
CAUTION:
Phono jack plugs are fragile. Do not pull
plugs from PC board by pulling coaxial cable.
CAUTION:
Trident Model 91S/92S units are Electrostatic
Discharge (ESD) sensitive instruments. Follow ESD han-
dling procedures on page 4 when servicing this equipment
to avoid circuit damage.
* Two wire (current shift) models only.
