SLT32 Level & Flow Monitor
  • Measure Level or Open Channel Flow
  • User-Friendly Calibration System
  • Isolated 4-20mA (1000 ohm)
  • False Echo Rejection
  • 3 Programmable Control Relays
  • Electrical Surge Protection
  • Intrinsically Safe Sensor Option
  • Self-Testing

Use this versatile instrument to continuously measure, display, transmit and control liquid level in storage tanks or pumping stations, or to monitor and totalize Open Channel Flow through any flume or weir. Mount the non-contacting ultrasonic sensor above the liquid being measured and install the watertight Electronics enclosure nearby. Features a user-friendly keypad calibration system, two digital displays, an isolated 4-20mA output and 3 programmable control relays.

Calibration is easy with the built-in 3 button keypad. The SLT32 offers simple menu selection of measurement units (gallons, liters etc.), calculates volume in horizontal round tanks, or flow rate (and total) through any flume or weir.

For hazardous locations, the ultrasonic sensor is rated Intrinsically Safe with an optional safety barrier. The standard PVC Sensor (optional Teflon) is rated for measurement ranges up to 32 ft/10 m, or use the optional PVC Sensor rated for 50 ft/15.6 m measurement range. Options include 3 additional control relays (6 total) and a built-in 50,000 point Data Logger.

SLT32 User's Guide (832KB Adobe Acrobat file)

SLT32 Brochure (921KB Adobe Acrobat file)

SLT32 Order Form (37KB Adobe Acrobat file)

Standard features include:

  • sensor - PZ32T, PVC and teflon, 32 ft / 10 m range
  • sensor cable - 25 ft / 7.6m coaxial
  • enclosure - watertight, dust tight NEMA4X (IP66) polycarbonate
  • programming - built-in 3 button keypad, Password protected
  • calibration - Level, Range or Open Channel Flow
  • displays - Level/Flow values - large 4-digit LCD Menu/Status/Totalizer - 16-digit alphanumeric
  • 3 relays - 5 ampere SPDT, programmable alarm and/or pump control modes, lead/lag pump alternation, failsafe/echo-loss, flow alarm, flow proportional pulse
  • temperature compensation - automatic
  • output - isolated 4-20mA (1000 ohm)
  • power input - 100-130VAC 50/60Hz, 7 watts maximum
  • electrical surge protection - sensor, AC power and 4-20mA output
  • 1 PC software utilities disk
  • 1 Manual - Installation and Operation


SCOPE: This specification covers a non-contacting ultrasonic Level/Flow Monitor as manufactured by Greyline Instruments, Massena New York / Long Sault, Ontario. This instrument shall provide for indicating, transmitting and control of the material level in a vessel or proximity of a target to the instrument sensor, and indicating, transmitting, and totalizing of the flow rate through a flume, weir, or other primary measuring device.


  1. Level/Flow Monitor to consist of an non-contacting ultrasonic sensor, connecting cable, and a remote enclosure with indicating, transmitting and controlling electronics.
  2. Measurement accuracy shall be ±0.25% of Range or 2 mm (0.08"), whichever is greater, and shall be automatically temperature compensated.
  3. Sensor cable length shall be as required by installation, not to exceed 500' (152 m).
  4. System shall have no moving parts and shall not contact the material being measured.
  5. Shall include PC software program disk to determine open channel flow calibration values for non-standard flumes and weirs.


  1. Sensor shall be constructed of PVC and Teflon.
  2. The sensor shall have a minimum deadband or blanking of 12" (305 mm) and a maximum range of 32 ft. (10 m), and have an operating frequency of 42 kHz with an ultrasonic beam angle of 8 Degrees.
  3. Sensor shall withstand accidental submersion to 20 psi.
  4. Sensor operating temperature shall be from -40°F to 150°F (-40°C to 65°C).
  5. Sensor shall include integral temperature sensor. Temperature sensors requiring separate mounting and wire runs shall not be accepted.


  1. Provide RG62AU coaxial cable 25' (7.6m) continuous length, with waterproof, potted bond to the Sensor head.
  2. Extended sensor cable shall be RG62AU coaxial to a maximum of 500' (152m). Cable shall be spliced with screw terminal connections in manufacturer's recommended steel NEMA4 Junction Box.
  3. Level and temperature signals shall be conducted on one single coaxial cable. Separate or multiple-conductor cables shall not be accepted.
  4. Sensor cable shall be installed in grounded metal conduit.


  1. The transmitter shall provide for field-calibration via built-in 3-key calibration system with menu selection of parameters. Systems requiring calibration by Parameter codes, BCD switches or external calibrators shall not be accepted.
  2. Calibration data shall be permanently stored through power interruptions without requirement of a back-up battery.
  3. Field calibration shall allow selection and automatic conversion of measurement units, measurement span and control relays.
  4. The transmitter shall provide for field calibration in user-selected Range, Level or Open Channel Flow modes. Flow mode shall allow calibration to common primary metering devices, plus allow entry of calibration formula for non-standard flumes, weirs or open channels.
  5. Transmitter shall permit field programmable damping to smooth output in turbulent level conditions, and programmable rejection time to disregard false signals from agitators, waves and spurious echoes.
  6. Transmitter operating temperature shall be from -5° to 140°F (-20° to 60°C).
  7. Transmitter shall have an isolated 4-20mA output into a 1000 ohm maximum load. Output shall allow field programmable offsets of 4mA and 20mA.
  8. Provide 3 control relay contacts rated 5 ampere SPDT. Relays shall be programmable for single set point alarms, dual set point pump control, pump alternation, temperature alarm, flow totalizer pulse and/or echo loss alarm.
  9. Provide a 4-digit LCD display scaled in user-selected engineering units.
  10. Provide a 16-digit alphanumeric display indicating units of measurement, calibrated full scale, flow totalizer, echo-loss condition and error messages.
  11. Transmitter shall be housed in a wall-mount, watertight NEMA4X enclosure with hinged, clear cover. Mounting hardware shall be included.
  12. Transmitter Displays indicating level and units of calibration, shall be visible without opening cover.
  13. Transmitter electronics shall be surge protected on AC power input, sensor and 4-20 mA output.
  14. Transmitter power input shall be 115VAC 50/60Hz with power consumption of 7 watts or less.


  1. Have 3 additional (6 total) control relays, rated 5 amp SPDT and programmable for single set point alarms, dual set point pump control, pump alternation, temperature alarm, flow totalizer pulse and/or echo loss alarm.
  2. Sensor, connecting cable and junction boxes shall be rated intrinsically safe to Class I,II,III, Div. I,II, Groups C,D,E,F,G.
  3. Have a thermostat controlled enclosure heater for Transmitter operation at temperatures below freezing.
  4. Have an all-Teflon sensor Model PZ32TE rated intrinsically safe when connected through an approved safety barrier, and rated for operation from -40°F to 170°F (-40°C to 76°C).
  5. Have a PVC and Teflon sensor Model PZ52T rated for measurement range on liquids up to 50 ft. (15.6 m).
  6. Have a PVC sensor Model PZ80 rated for measurement range on liquids up to 80 ft. (25 m).
  7. Have manufacturer's recommended enclosure sunscreen to permit Transmitter mounting in direct sunlight.
  8. Have manufacturer's recommended Sensor sunscreen to permit temperature-compensated Sensor mounting in direct sunlight.
  9. Have manufacturer's recommended Panel Mount Flange assembly for enclosure installation.
  10. Have a built-in 50,000 point data logger with Windows™ software for data retrieval, graphing and export. Data Logger shall include RS232 output and serial cable for direct PC connection, or dial-up connection through modems.
  11. Transmitter power input shall be 200-260VAC 50/60Hz with maximum power consumption of 7 watts or less.
  12. Transmitter power input shall be 24VDC with maximum power consumption of 6 watts or less.
  13. Transmitter power input shall be 12VDC (battery power) with maximum power consumption of 6 watts or less.


Level/Flow Monitor shall be Model SLT32 as manufactured by Greyline Instruments Inc. and shall be warranted against defects in materials and workmanship for one year.