"Flashlite"™ Pressure Sensor (H-3531)


The WaterLOG® "FlashLite"™ Pressure Sensor (H-3531) is an NIST traceable pressure sensor designed to directly measure dry gas with accuracy greater than 0.02% FSO. It's accuracy over temperature range exceeds ±0.01 ft. (3 mm) of water with a 15 PSI sensor, and it has built-in temperature compensation. You'll enjoy it's user friendly RS-232 menu interface for programming, and that the SDI-12 output provides measurment data in user-defined units. Compatible with the H-3551 Bubbler and SDI-12 data logger, this Sensor combines high accuracy and low cost making it perfect for water level measurement in a bubble gage at any site.

  • Features
  • Specifications

Accurately measure river, lake, well, ocean and waste water level in a bubble gage with the WaterLOG® "FlashLite"™ Pressure Sensor (H-3531).

Other Features

  • RS-485 programmable for MODBUS slave or H-3551 control
  • Standard mode outputs: SDI-12, 4-20mA, RS-485 and Rs-232
  • Optional outputs: 0-5V and Quadrature
  • Programmable continuous outputs
  • Low current operation (less than 1mA standby)
  • Extended SDI-12 command for setting the stage to the current water elevation or pressure
  • Programmable averaging
Accuracy / Resolution

Less than or equal to 0.02% of full scale output (FSO) over temperature range
Pressure Hysteresis Less than 0.01% of FSO
Linearity Less than 0.02% deviation
Temperature Internal temperature ±1° C over tem­perature range
Long-term stability Drift is less than ±0.05% of FSO per year
Standard Pressure Ranges are 15 PSI and 30 PSI
Custom calibration ranges available

1 part in 1,000,000 (0.0001%)
Temperature 1 part in 1,000,000 (0.0001%)
0 to 15 PSI 0 to 34.6 ft. (10.54 m) ±0.007 ft. (2.1 mm)
0 to 30 PSI 0 to 69.20 ft (21 m) ±0.014 ft. (4.26 mm)

4.76 in W x 4.76 in L x 2.5 in H

12 mm W x 12 mm L x 6.35 mm H

Material Housing: Fiberglass
Atmospheric Vent: Sintered bronze #10-32

Weight 2 lbs (.91 kg)

7-pin Circular: Power, SDI-12, 4-20mA and RS-485

3-pin Circular: RS-232 Communications port
Cables: Main Connector cable with 6 ft (1.83 m) pigtail is provided. RS-232 Connector cable optional
Connectors: Sealed Bendix type circular
Pressure Inlet: 1/8 in. (38.1 mm) female NPT
Power Requirements
Voltage Input

10 to 16.5 V DC
Supply Current Standby: 700uA max
Active: 80mA max
Surge Protection Built in, 1.5 KVA
Baud Rate

Protocol SDI-12 V1.3, 7-bit even parity, 1 stop bit
Output Voltage Level

High: 3.5 volts (Min)

Low: 0.8 volts (Max)
Response Time 6-seconds measurements sequence (programmable)
RS-485 Interface
Baud Rate

Programmable (default - 9600)
Protocol Modbus RTU/H-355
Control Port RS-485
RS-232 Interface


RS-232, 8bit, No Parity, 1 stop bit
Baud Rate 9600
0-5V Analog Output (optional)

1 part in 4096 (0.02%)
Accuracy ±0.025%
4-20mA Output

4-20mA, optically isolated .75 ft (2.67 m)
Loop Voltage 8.0V min 35V max
Resolution 1 part in 4096 (0.02%)
Accuracy ±0.025%
Quadrature Output (Optional)
Output Voltage Low: 0.4 (max)@ -5mA
High: 2.5 (min)@ 5mA
General Specifications
Operating Temperature -40 ° to +60 ° C
Compensated Range -40 ° to +60 ° C
Storage Temperature -40 ° to +80 ° C
Pressure Overload Less than 2 times the rated pressure
Media Capability Non-corrosive dry gases only
Rating NEMA 4 Enclosure
IP Rating IP62 (Dust protection and falling water resistant)
Warranty The WaterLOG® H-3531"FlashLite"™ Pressure Sensor is warranted against defects in materials and workmanship for twenty-four months from date of shipment.

Options & Accessories


3-Conductor Interface Cable; RS-232


7-Conductor Interface Cable; Power, SDI-12, Control


Orifice Line (1000 ft. minimum)


Installation Kit (includes 2 - 1/8" NPT to 1/8" tube fittings, 1 - 1/8" NPT to 3/8" tube fitting, and 6 ft. 1/8" copper tubing)