Hanna Conductivity/TDS/pH/Temp Monitor – HI 991404

The wall mountable Hanna Combo HI 991404 series meters are designed for continuous, high accuracy pH, EC/TDS and temperature measurements. These microprocessor indicators continuously monitor the three most important nutrient parameters in hydroponics, greenhouses and horticultural applications with a single instrument. These indicators feature a large, dual-level, backlit LCD to give you instantaneous readings of pH, EC or TDS and temperature, even from a distance.


At startup, these indicators perform a self-check to assure proper working condition. HI 991404 stability indicator and hold features prompt the user when to take the reading and freezes the display for easy and accurate recording.


Calibration and temperature compensation is automatic, while the EC/TDS conversion factor and temperature coefficient (ß) are user adjustable for application-specific measurements.


These instruments are supplied with an advanced, non-clogging double junction pH electrode and a rugged conductivity probe that will withstand even the most aggressive environments. The instruments are powered by a 12 Vdc transformer and are easy to install and use, making them ideal for all continuously monitoring applications.


The meters are supplied with:


  • HI 1293D pH electrode
  • HI 7630 fixed EC probe
  • pH 4.01 and 7.01 buffer solutions (20 mL each)
  • 12.88 mS/cm calibration solution (20 mL), for HI 991404
  • 12 Vdc power adapter and instructions

Please note that continuous meters, will need their probes cleaned regularly to make sure that they don’t get fouled up, its best to clean them at least once a month (minimum) for half an hour in Hanna HI-7061 General Purpose cleaning solution. To clean them we sell a cleaning solution that you pop the probe in and leave. It might seem like a pain, but the more often you clean your probe, the longer the life expectancy and the more accurate readings you get. Probe life can vary six months with no cleaning, up to one to two years if they are cleaned and maintained regularly.




Product Specification Summary

Range pH 0.0 to 14.0 pH
Range EC 0 to 3999 µS/cm
Range TDS 0 to 2000 ppm (mg/L)
Range Temperature 0.0 to 60.0°C (32 to 140°F)
Resolution pH 0.1 pH
Resolution EC 1 µS/cm
Resolution TDS 1 ppm
Resolution Temperature 0.1°C (0.1°F)
Accuracy pH ±0.1 pH
Accuracy EC/TDS ±2% F.S.
Accuracy Temperature ±0.5°C (±1°F)
Temperature Compensation pH: automatic
EC/TDS: automatic with ß adjustable from 0.0 to 2.4%/°C
Calibration pH: automatic, 1 or 2 points with 2 sets of memorised buffers;
EC/TDS: automatic, 1 point
pH Electrode HI 1293D (included)
EC/TDS Probe HI 7630 (fixed)
EC/TDS Conversion Factor adjustable from 0.45 to 1.00
Environment 0 to 50°C (32 to 122°F); RH max 95%
Input Impedance 1012 Ohm
Power Supply 12 Vdc power adapter (included)
Dimensions 160 x 105 x 31 mm (6.3 x 4.1 x 1.2″)
Weight 190 g (6.7 oz.)