Omni Instruments
contact icon+44 (0) 1382 443000
+44 (0) 845 9000 601

Contact our technical sales team now to discuss your requirements

help icon
MY BASKET basket arrow


My Cart

You have no items in your shopping cart.

Click basket to edit.


Latest added news blog
MSR175 Shock Transportation Data Logger
Kenny Laidlaw
Oct 01,2018
The MSR175 shock transportation data logger is the newest miniature logger from MSR.  The MSR175 more >
MaxiMet GMX100 Optical Rain Sensor
  • MaxiMet GMX100 Optical Rain Sensor

GMX100 Optical Rain Sensor

Quick Overview

The GMX100 optical rain sensor is from the MaxiMet range of compact weather stations. The GMX100 features an integrated optical rain gauge and heater. The rain sensor automatically senses precipitation hitting its surface and uses algorithms based on the size and number of drops to determine rainfall and intensity. The GMX100 then provides readings for rainfall intensity, 24Hr rainfall totals and rainfall Y/N via RS232, RS485, RS422, SDI-12, NMEA and MODBUS serial outputs, or an optional analogue output. Unlike a tipping rain bucket, the GMX100 has no moving parts, preventing any false readings caused by movement. Power supply 5-30vDC, current consumption 80mA.
View Options


The GMX100 is a precipitation sensor in the MaxiMet range of compact weather stations and features an optical rain sensor. The sensor consists of an optical infra-red beam sensor. Infra-red beams bounce off the inner optical surface between transmitters and receivers. Depending on rain drop levels the intensity of the beams change and internal digital signal processing allows a measurement of rain levels to be made. Algorithms then interpret the data of drop size and quantity to determine rain fall totals and intensity. The sensor can therefore provide data for exactly when rain starts and stops as well as the amount and intensity of the rainfall. The sensor also includes an integrated heater to ensure the sensor is kept clear of dew and condensation. 

The GMX100 offers additional benefits over traditional tipping rain bucket rain sensors. Counting tips may not be accurate as rain may stop before the lever has tipped. When the next period of rain begins it may take no more than one or two drops to tip the lever. Tipping buckets also tend to underestimate the amount of rainfall, ie. not recording all of it, particularly in snowfall, heavy rainfall events or in high wind conditions. Finally, tipping rain buckets can be subject to vibration, whilst the GMX has no moving parts and isn't affected by any movement. Rain buckets that are not securely mounted, or used in an offshore application, may be subject to false rain measurements due to motion causing the balance to tip.

The GMX100 has been designed as a complete rain sensor suitable for any installations, including those that may not be suitable for traditional rain sensors eg. Marine applications, where the motion on the sea could provide false values, or extreme environments where rainfall totals may not otherwise be accurately measured. This sensor can be easily integrated into remote weather station, weather buoys or fixed installations to work as a stand alone rainfall sensor or as part of a larger environmental monitoring system.

GMX100 Dimensional Drawing


  • Lightweight and Robust Rain Sensor
  • Provides: Rainfall Totals, Intensity and rainfall Y/N readings
  • Rainfall totals available in mm or inches
  • Integrated Heater
  • No Moving Parts
  • Low Power Mode
  • Bolt fittings supplied for securing the unit to a vertical pipe of diameter 44.45mm
  • MetSet and MetView software include

Precipitation Total.
Outputs Precipitation (Rain) Total reading, this is a one minute updated accumulated rain reading output once per second (with default output rate setting at 1Hz).
Is set to zero on MaxiMet power up.
Is set to zero when the clock reads 23:59:59 to 00 (midnight) and is the default setting.
For continuous measurement turn off Auto-reset of Total Precipitation using MetSet. Result e.g. 00000.4 (millimetres default).

Precipitation Intensity.
Outputs Precipitation (Rain) Intensity.
It is the sum of the last sixty lots of 1 minute accumulated Rain data. A new sum measurement is generated every minute.
It will be set to zero on MaxiMet power up.
Result e.g. 000.2 (millimetres default).

Precipitation Status.
Outputs Precipitation (Rain) Status as N or Y (No or Yes).
Changes N to Y when total precipitation is incremented.
Changes Y to N when total precipitation has not incremented in the last 60 seconds.
Result e.g. N (or Y).

GMX100 Data Logging Options

Measurement Type: Optical
Output Range: 0 to >300mm/hr
Resolution: 0.2mm
Repeatibility: 3%
Sampling Rate: 1 Hz
Units: mm/hr, mm Total, mm/24Hr. inchs/hr, inchs Total, inchs/24Hr

Output Rate: 1/s, 1/min, 1/hr
Digital Comms Modes: Serial RS232, RS422, RS485, SDI-12, NMEA, Modbus, ASCII
Analogue Outputs: Available via separate optional device

Power Supply: 5 to 30vDC
Power (Nominal) 12vDC: 80mA continuous high mode. 0.7mA eco-power mode (1 hour polled)

Environmental Conditions
IP Rating: IP66
Operational Temperature Range: -40 to +70°C
EMC Standard: BS EN 61326:2013 FCC CFR47 Parts 15:109
CE Marking: Yes
Weight: 0.3Kg
Country of Origin: UK

Availability: Stock Item


Components / Downloads

For further information, technical advice, or a quotation please call or email us. If you are not sure which product you need one of our technical sales advisors will be happy to discuss your application. We also accept company purchase orders by fax or post. Credit card orders can also be placed over the phone for any product.

Portable Tripod
Weather station tripod mounting kit with 2m pole. The legs on this tripod are not adjustable for uneven surfaces and ground should be levelled prior to installation. ¼" stake kit (M-SKB), ½" Stake kit (M-SKA), Guy wire kit (M-GWA) and Grounding kit (M-GKA) are available separately.
or call us for a quote
Mounting Accessories
Mounting adaptor for connecting the WindSonic wind sensors or MaxiMet compact weather stations to the M-TPB tripod. Provides a direct mounting to the top of the tripod for an unobstructed placement of the mounted sensors. Ideal for solar radiation, wind and rain sensors.
or call us for a quote
Anodized Aluminium Bracket for mounting to pole and wall. Includes an aluminium sensor adaptor for WindSonic or MaxiMet, fully anodised to reduce corrosion. The Bracket uses a mounting clamp suitable for attaching to a vertical pipe with a diameter of 30-58mm. When mounting the MaxiMet, consider the position, orientation and alignment of the unit. Mount at the top of a pipe to ensure a clear unobstructed measurement view. Kit includes stainless steel mounting bolts, multiple earth points and wall / pole mounting kit
View FileData Sheet
   Size: (947.37 KB)
or call us for a quote
Cable assembly to connect Windsonic or MaxiMet unit to external data logger or display. Includes inline multipole connector for WindSonic or MaxiMet and flying leads, cable length 6.5 metres. Other lengths available on request.
or call us for a quote
MaxiMet Configuration Cable
MaxiMet 1.8 Metre RS232 to USB converter including 5vDC power and communication configuration cable (9 way MaxiMet connector fitted one end and USB connector at the other end). Simplifies the connection of the MaxiMet units to a PC
or call us for a quote
WindSonic Accessories
Spare 9 way mating connector. Suitable for all WindSonic plastic versions, WindSonic M Non-Analogue and MaxiMet sensor and weather stations.
or call us for a quote