FAQ No. FAQ00751
Are there any precautions to observe when
controlling pure water with 61F Floatless Level Controller?
The conductivity or specific resistance is a factor in the selection of a
61F Controller. Measure the interelectrode resistance to select the proper
model accurately. A 61F Controller can be used if the measured value is
within the "interelectrode operate resistance" listed in the
Specifications Table of the Datasheets (Catalog Number: F030).
When the resistance range is measured with an instrument such as a
multimeter, the interelectrode resistance cannot be measured accurately
because the electrode voltage is DC. Always use the 61F Controller's
interelectrode voltage (AC) to measure the interelectrode resistance.
Measuring the Interelectrode Resistance
When the Controller is not operating properly even though it is wired
properly, measure the interelectrode resistance. In this case, use a
voltmeter and ammeter to measure the voltage drop, as shown in the
The interelectrode resistance (liquid
resistance between E1 and E3) can be calculated with the following
R = V/I
R: Liquid resistance between the electrodes (kΩ)
V: Voltmeterís displayed value (V)
I: Ammeterís displayed value (mA) Select an appropriate 61F Controller
model based on the value of R.
The following list can be used as a guide to
select a 61F Controller model from the conductivity.
0.5 to 2 μS (microsiemens) → 61F-UHS (0 to 1 MΩ)
2 to 5 μS → 61F-GP-NH3 (0 to 200 kΩ)
5 to 10 μS → 61F-GH (0 to 70 kΩ)
61F-GP-NH (0 to 40 kΩ)
61F-GPN-V50 (0 to 50 kΩ)
15 to 25 μS → 0 to 4 kΩ for standard general-purpose applications
1. With the 61F-HSL Ultra High-sensitivity model, a DC current flows
through the electrodes. If the electrodes are usually submerged, galvanic
corrosion will occur, so the Ultra High-sensitivity model cannot be used
for control. Applications are restricted to upper limit alarms and leakage
detection (e.g., errors, external tank overflow detection, etc.)
2. For pure water over 1 MΩ (18 MΩ model
also available), use a K7L
Liquid Leakage Sensor Amplifier or Electrostatic Capacitance Level Switch (such
as the E7A or E7M).
Other Level Controller
What kind of wiring is best to combine a 61F-GP-N Controller and float switch?
Is it possible to connect more than one 61F Controller to the same electrodes and share the electrodes?
When voltage is applied to the 61F Controller, it operates regardless of the actual liquid level. What is the cause of the problem and how can it be corrected?