Paquin is spotlighting the P41 Ultrasonic Level Sensor, an economical, non-contact level transmitter with a built-in visual display. The P41 measures the level of liquids and dry bulk materials from above, using ultrasonic pulses rather than a probe in the product. It covers ranges from 0–16 ft to 0–164 ft (5 to 50 m), and its outputs, relays and mounting style can be tailored to everything from small process tanks to large storage silos.
Why measure level without contact
Many level technologies rely on a sensing element that sits in, or touches, the material being measured. That approach works well in clean water, but it can be a poor fit for corrosive chemicals, sticky or abrasive products, hygienic processes and dry bulk solids. In those conditions, a contacting sensor may need frequent cleaning, may wear prematurely, or may be unsuitable altogether.
A non-contact ultrasonic sensor avoids these issues by mounting above the material and measuring the distance to its surface. Nothing is immersed, so contamination, wear and fouling risks are reduced. According to its datasheet, the P41 also maintains its accuracy regardless of the material's density or dielectric properties, which makes it a versatile choice when one sensor type needs to cover many different media.
How the P41 ultrasonic level sensor works
The P41's transducer emits short ultrasonic pulses in the 35 to 70 kHz range toward the product surface. The pulses reflect back to the transducer, and the sensor measures the elapsed time. Because sound travels at a known speed, the distance (D) to the surface is calculated from that time. When the empty distance of the vessel (E) has been entered, the level (L) is simply E minus D.
Two features help keep that calculation reliable in real installations:
- Echo processing. The P41's signal processing software identifies the true level echo among false echoes, such as reflections from internal vessel features.
- Temperature compensation. The speed of sound changes with temperature. An integrated NTC temperature sensor measures conditions in the vessel and corrects the timing calculation accordingly.
Setup is equally straightforward. Because the level signal is generated from the vessel dimensions you enter, there is no need to fill the vessel to adjust the sensor. As with all ultrasonic level instruments, the installation should allow for the blind area directly beneath the sensor face, where measurement is not possible.
Standard or remote: choosing a configuration
The P41 is available in two formats. The standard version combines the transducer, electronics and display in a single unit. The remote version separates the transducer from a wall-mounted receiver with its own display, which is useful when the top of the vessel is difficult to reach.
| Feature | Standard (all-in-one) | Remote (wall-mount receiver) |
|---|---|---|
| Display location | On the sensor | On the wall-mounted receiver |
| Analog output | 4–20 mA, four-wire (510 Ω load) or two-wire (250 Ω load) | 4–20 mA, four-wire (510 Ω load) |
| Alarm relays | None or 2 | None, 2 or 4 |
| Power consumption at 24 VDC (no relays) | 80 mA four-wire; 30 mA two-wire | 100 mA |
Outputs, relays and display
Every P41 provides a 4–20 mA analog output, and RS232 or RS485 serial communication can be added for integration with control and monitoring systems. Optional relays, rated up to 30 VDC / 5 A, can be programmed for high-level, low-level or other alarm and control functions. This allows the P41 to measure level and act on it, for example by signaling a pump controller or triggering an alarm, without a separate level switch. The LED display shows the reading locally for operators on the plant floor.
For corrosive or aggressive media, the sensor face can be specified in PTFE instead of the standard ABS.
Applications
- Water treatment and wastewater
- Food and beverage
- Pharmaceuticals
- Chemical refining and manufacturing
- Agriculture
- Mining and bulk materials
Key specifications (snapshot)
| Parameter | Value |
|---|---|
| Measuring principle | Non-contact ultrasonic, 35–70 kHz pulses |
| Measuring ranges | 0–16, 32, 49, 65, 98, 131 or 164 ft (5 to 50 m); custom ranges available |
| Accuracy | 0.5% |
| Resolution | 3 mm or 0.1% |
| Media | Liquids and dry bulk solids |
| Output | 4–20 mA; optional RS232 or RS485 |
| Relays | Up to 4 (remote version), programmable, max. 30 VDC / 5 A |
| Power supply | 24 VDC |
| Temperature compensation | Integrated NTC sensor |
| Operating temperature | Housing -4 to 140°F (-20 to 60°C); probe -4 to 176°F (-20 to 80°C) |
| Protection class | Display IP65; probe IP68 |
| Materials | ABS housing; ABS or PTFE sensor face |
| Process connection | Male thread, sized by range (G1½" up to M108 x 2) |
Dimensions, pin-outs and wiring for both versions are covered in the P41 datasheet (PDF).
Configure a P41 for your vessel
If your application only needs to detect a single level point rather than measure continuously, the P421 Ultrasonic Level Switch brings non-contact sensing to liquids, pastes and slurries. Paquin's full level measurement range covers switches, submersible sensors and transmitters for nearly any vessel.
A P41 is specified by its measuring range, output, relay count, standard or remote format and sensor face material. Share a few details about your vessel through the P41 product page: the height, the material being measured and how you want to use the signal. Paquin will recommend a configuration and send a quotation.
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