High-frequency measurement delivers precise, drift-free performance across conductive and non-conductive materials.
Provides independent control for high/low alarms, pump-up/pump-down operation, or overflow protection—all in one device.
Offers both continuous 4–20 mA or 0–10 V output and discrete relay control—reducing the need for separate instruments.
Allows fine-tuned calibration and stable operation with minimal maintenance.
Relays de-energize automatically on fault or power loss for added operational safety.
Compensates for buildup or conductive coating on probes, maintaining reliable readings in sticky or viscous media.
Supports up to 1 mile (1.6 km) of cable between probe and electronics for remote or hard-to-access tanks.
| Parameter | Description |
|---|---|
|
Measurement Technology |
RF Capacitance, remote preamplifier with high-frequency excitation (~1 MHz) |
|
Output Signal |
4–20 mA DC and 0–10 V DC (standard); optional 20–4 mA or 10–0 V inverted output |
|
Relay Outputs |
Dual SPDT (5 A @ 115 VAC, 3 A @ 230 VAC or 26 VDC non-inductive); independent setpoints and adjustable differential |
|
Power Supply |
115 VAC (100–130 V) or 230 VAC (200–260 V), 50–60 Hz |
|
Fail-Safe Modes
|
Selectable High or Low level (relay de-energized above or below setpoint) |
|
Setpoint Range
|
0.08 in. to 200 ft water equivalent (0.5–30,000 pF adjustable) |
|
Analog Accuracy
|
±0.1% of setting up to 1,000 pF |
|
Temperature Stability
|
±0.01%/°F (±0.018%/°C) |
|
Response Time
|
0.5 sec standard; optional 50 ms–10 sec adjustable delay |
|
Operating Temperature
|
–40 °F to +160 °F (–40 °C to +71 °C) for preamp and electronics |
|
Cable Length (Probe to Electronics)
|
Up to 1 mile (1.6 km) using shielded twisted pair |
|
Probe Options
|
Rigid or flexible probes in 316 SS, Teflon®, or Kynar® insulation |
|
Housing |
Explosion-proof cast aluminum, NEMA 4, 5, 7, 9, 12 |
|
Enclosure Approvals
|
NEC Class I, Groups C & D; Class II, Groups E, F, G |
|
Indicators
|
Red: Level ≥ setpoint; Yellow: Relay energized; Green: Probe/wiring OK |
|
Accessories
|
AFI-150 / DFI-150 field indicators, remote calibration tools, and mounting kits |
Have a look at the flyer to get all the tech specs and product features.
Brochure
Read the manual for detailed information and instructions.
Manual
Check out a sample cert from our calibration lab.
Certificate
If you have a question that we have not covered then just get in touch and we’ll be happy to help.
We have tried to answer the most common questions we are asked here.
It combines continuous analog measurement with dual relay control in a single, explosion-proof device—reducing the need for separate instruments.
Yes. Its coating-rejection circuitry compensates for conductive or sticky buildup, ensuring stable measurement accuracy.
Up to 1 mile (1.6 km) using shielded twisted-pair cable, ideal for remote or inaccessible tanks.
Absolutely. The 421 is rated NEC Class I, Div 1 and Class II, Div 1, with explosion-proof housing and fail-safe relay modes.
Yes. The 421 offers 4–20 mA or 0–10 V DC analog output alongside dual SPDT relays for high/low alarms or pump control.
The dual SPDT relays allow the transmitter to perform basic process control in addition to continuous measurement. For instance, one relay can be set as a high-level alarm (shutdown) and the other as a low-level setpoint (pump-on), consolidating control logic and continuous signal output into a single instrument.
Common applications include chemical processing, wastewater treatment, food and beverage, and bulk storage systems where both measurement and alarm control are required.
No. The transmitter features temperature-stable electronics with a stability rating of 0.01% per °F. This high level of thermal compensation ensures that the analog output remains accurate and consistent, even in extreme outdoor or process temperature variations, minimizing the need for field recalibration.