Industrial Grade TDS Controller with Proportional Fertilizer Dosing for Hydroponics Applications
HI 9934 is a wall mounted meter that controls TDS in the 0 to 1999 ppm (mg/L) range through a single set point for dosage of fertilizers. The proportional control can be fine tuned through the time cycle between 0 to 90 seconds and the proportional band from 0 to 400 ppm. Coarse and fine as well as a slope trimmer make for an accurate setting and calibration. A pump or electrovalve can be powered through the terminal. In addition to the set point relay, HI 9934 also provides for an alarm relay. The alarm is activated when the measurements exceed the set point by a user selectable margin in the 50 to 450 mg/L (ppm) range. The alarm also triggers if, due to a malfunction, the continuous dosing time exceeds the operator adjustable period of 1 to 10 minutes. The alarm can be configured in either normally-closed or normally-open position and turned off during maintenance.
HI 9934 also provides an isolated output signal which is user selectable between
0-20 or 4-20 mA.
HANNA instruments four-ring TDS probes with incorporated temperature sensor and DIN connector can be quickly attached to the controller. Readings are automatically compensated for temperature variations in the 0 to 50°C (32 to 122°F) range.
The extractable terminal wiring is through the side of the meter with washers and grommets. The compartment containing the connections is enclosed behind a fire-retardant ABS panel.
Range 0 to 1999 ppm (mg/L)
Resolution 1 ppm (mg/L)
Accuracy @ 20°C ±2% f.s.
Calibration through “ZERO CAL” and “SLOPE CAL” trimmers
Setpoint from 0 to 1999 ppm (mg/L)
Factor 0.65 mg/L (ppm) = 1 µS/cm
Compensation automatic, 0 to 50°C (32 to 122°F) with ß = 2%/°C
Recorder Output selectable at 0-20 mA or 4-20 mA (isolated)
Control TDS from 0 to 400 ppm and time cycle from 0 to 90 seconds
Alarm Contact terminals 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 TDS exceeds by more than the user- selectable interval (0 to 400 ppm) from the set point or due to overdosage
Dosing Terminals relay (115 to 240V, max.2A, 1,000,000 strokes) are activated whenever TDS falls below the set point
Probe four-ring potentiometric with built-in temperature sensor (not included)
Power Supply ±10% 115 VAC or 230 VAC; 50/60 Hz
Environment -10 to 50°C (14 to 122°F); RH max 95% non-condensing
Case Material fiber-reinforced, self-extinguishing ABS
Dimensions 221 x 181 x 86 mm (8.7 x 7.1 x 3.4’’)
Weight 1.6 kg (3.5 lb.)
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