Hanna HI 9935-1 pH and TDS Proportional Control for Fertigation

Hanna HI 9935-1 pH and TDS Proportional Control for Fertigation


HI 9935 is a pH and TDS controller for fertilizer solution dosage in hydroponics.

HI 9935 measures pH from 0 to 14 and TDS from 0 to 1999 mg/L (ppm). Two separate set points can be adjusted from 4 to 7 pH and 900 to 1800 ppm (mg/L). The relays are activated when the pH exceeds the set point or TDS falls below the desired value. Two pumps or electrovalves can be wired directly to the controller and be powered through the terminals. Independent proportional settings for pH and TDS can be adjusted from 0 to 90 seconds, 0 to 2.0 for pH and 0 to 400 mg/L (ppm) for TDS. A matching pin/ground probe can be connected to the appropriate terminals to extend electrode life and eliminate interference.

HI 9935 provides for an alarm relay which is activated in several circumstances. These include when the pH is below the set points in the operator adjustable threshold of 0.5 to 2.5 pH, or similarly, TDS exceeding the set point by a value in the 50 to 450 mg/L (ppm) range. The alarm also goes off if the pH and/or TDS are not corrected within the operator determined time frame of 1 to 10 minutes. Moreover, the alarm configuration is switchable from a normally-closed to a normally-open state or turned off during maintenance. The fertilization status can be ascertained from a distance through dosage and alarm LED's.

HI 9935 accepts pH electrodes with a BNC connector and TDS probes with a DIN connector.


RangepH0.00 to 14.00 pH
TDS0 to 1999 ppm (mg/L)
ResolutionpH0.01 pH
TDS1 ppm (mg/L)
Accuracy @ 20CpH0.02 pH
TDS2% f.s.
Input Impedance1012 Ohm
Calibrationthrough "OFFSET" and "SLOPE" trimmers for pH, and "ZERO CAL" and "SLOPE CAL" for TDS
Setpointfrom 4.0 to 7.0 pH and 900 to 1800 ppm (mg/L)
TDS Conversion
0.65 mg/L (ppm) = 1 S/cm
Compensation (TDS)
automatic, 0 to 50C (32 to 122F) with = 2%/C
two independent controls: pH from 0.0 to 2.0 and TDS from 0.0 to 400 ppm (mg/L) with two separate time cycles from 0 to 90 seconds
Alarm Contactterminals can be configured as normally open or normally closed (isolated output max. 2A, max. 240V, resistive load, 1,000,000 strokes). The alarm is activated if pH falls below the set point by the user selectable interval (0 to 2 pH),or TDS exceeds the set point by more than the user selectable interval (0 to 400 ppm) or due to overdosage
Dosing Terminalstwo sets of independent terminals (115 to 240V, max. 2A, 1,000,000 strokes) are activated whenever pH exceeds the pH set point and for the TDS falls below the TDS set point
Probeany combination pH electrode with a universal BNC connector and HANNA TDS four-ring potentiometric probe with built-in temperature sensor and DIN VVxX

Item Number: 135423
Manufacturer: Hanna Instruments
Manufacturer's Part Number: HI 9935-1


pdf file Instruction Manual

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