A transmitter converts a physical quantity on the line into a 4–20 mA / 0–10 V industrial standard signal for PLCs, DCSs and indicators. The item on this page is the Fisher DLC3010 digital level controller: it mounts on a displacer level sensor, measures level, interface or density, and outputs 4–20 mA + HART. Differential pressure (DP) transmitters are available on request.
A transmitter is the “signal translator” between the production line and the control system. It takes the raw physical quantity picked up by the sensing element (differential pressure, displacement, level, temperature), amplifies and linearizes it, and converts it into a 4–20 mA or 0–10 V industrial standard signal. Without a transmitter, the PLC, DCS and indicators cannot read line data.
The DLC3010 on this page is a digital level controller (a displacer-type level transmitter, not a DP transmitter). The two types compare as follows: a DP transmitter measures the pressure difference between two ports and is common for flow calculation, level measurement and filter clogging alarms (on request); a displacer level transmitter mounts on a displacer level sensor (Fisher 249 series). Changes in level, interface or density change the displacer’s buoyancy and turn a torque tube; the DLC3010 measures the angle with a Hall sensor and outputs 4–20 mA + HART, for tank level monitoring with corrosive, hot or crystallizing media. We supply products from many brands and compatible solutions for semiconductor plants in Hsinchu Science Park, chemical processes and cleanroom differential pressure monitoring.
Specifications
| Item | DP transmitter (on request) | Displacer level transmitter (DLC3010 on this page) |
|---|---|---|
| Measuring principle | Differential pressure sensing between two ports (capacitive / silicon resonant) | Displacer buoyancy turns a torque tube; Hall sensor measures the angle (DLC3010) |
| Output | 4–20 mA (2-wire) or HART | 4–20 mA (2-wire) + HART |
| Power | 24 VDC | 24 VDC |
| Range | -100 kPa to +100 kPa (by model) | Depends on displacer length and tank height (general case; each case needs checking) |
| Accuracy | ±0.075% to ±0.5% FS | ±0.5% to ±1% FS |
| Process connection | 1/2″ NPT, flanged | Flanged (to the tank) |
| Enclosure | IP65 / IP67 | IP65 / IP67 |
| Typical use | Flow, level, filter clogging | Tank level (corrosive, hot, crystallizing media) |
Applications
Transmitters are the basic nodes of process control; without reliable signal input, PLC and DCS control logic means nothing. Semiconductor front-end processes, chemical supply, cleanroom pressure and facility HVAC in Hsinchu Science Park all use transmitters heavily. Four common applications:
- Cleanroom differential pressure monitoring: cleanrooms stay clean through positive pressure, with the room slightly above corridors and adjacent non-clean areas so outside dust cannot flow in. A DP transmitter measures the room-to-outside pressure difference continuously (typically 5–15 Pa) and sends it to the BAS (building automation system); when the difference drops, the supply fan speeds up automatically (DP transmitters on request).
- Chemical tank level monitoring: level and interface measurement in strong acid and alkali tanks in chemical plants and in H₂SO₄ / NH₄OH chemical drums in semiconductor plants. The displacer sits in the liquid; level changes alter its buoyancy and turn the torque tube, and the DLC3010 measures the angle and outputs 4–20 mA + HART to the DCS for automatic refill at the low setpoint and automatic valve closing at the high setpoint.
- HEPA / filter clogging alarms: cleanroom HEPA filters, compressed air dryers and exhaust scrubbers all need filter clogging monitoring. A DP transmitter spans the pressure taps before and after the filter; when the difference passes a set threshold (for example 30 Pa new, 150 Pa dirty), it sends a maintenance alarm so the filter gets changed (DP transmitters on request).
- Flow measurement (orifice plate + DP): large-pipe flow measurement (process cooling water, CDA compressed air mains, chemical supply mains) often uses an orifice plate with a DP transmitter. The orifice creates a local restriction and pressure drop; the DP transmitter measures it and converts it to flow by formula. It costs less than an insertion flowmeter and suits high flows (DP transmitters on request).
Selection points
| Item | Suggestion | Note |
|---|---|---|
| Range | 1.5–2 times the actual operating value | Too large a range sacrifices accuracy |
| Accuracy class | General ±0.5% FS; critical processes ±0.1% FS or better | Higher accuracy costs more |
| Output | 4–20 mA for long runs and industrial lines | 0–10 V for short indoor runs |
| Process connection | NPT / flange to match the pipe or tank | Must match existing piping |
| Enclosure | IP67 or higher outdoors or in damp areas; Ex certification in hazardous areas | Chemical areas often need Ex d / Ex ia |
| Media compatibility | Hastelloy / tantalum diaphragm for corrosive media | Avoid direct stainless steel contact with strong acids and alkalis |
Sensor vs transmitter: why industrial lines separate the two
Many engineers use “sensor” and “transmitter” interchangeably, but they do different jobs:
| Item | Sensor | Transmitter |
|---|---|---|
| Role | Senses the physical quantity | Amplifies and converts the signal |
| Output | Millivolts, resistance, frequency (non-standard) | 4–20 mA / 0–10 V / HART (industrial standard) |
| Connects straight to a PLC? | No (needs signal conditioning) | Yes (straight to an analog input card) |
| Common examples | Strain gauge, thermocouple, LVDT | Integrated amplification, linearization, temperature compensation |
In practice: most modern products are “integrated transmitters” that combine sensor and transmitter in one housing, though inside they are still two stages. Split designs (sensor at the process, transmitter in the control panel) are common in high-temperature, highly corrosive or hazardous-area processes, keeping the transmitter in the safe area away from harsh conditions.
More on DP transmitters: level in closed tanks
Level measurement: measure the pressure difference between the bottom of a closed tank and the vapor space at the top, and convert it to liquid column height. Needs temperature and density compensation. Advantages: no contact with the liquid surface, works with corrosive media and sealed tanks. Typical uses: sealed chemical tanks and pressurized reactor levels (DP transmitters on request).
Displacer level vs other level measurement methods
A displacer level gauge measures tank level: level changes alter the displacer’s buoyancy and turn the torque tube, and a level controller (such as the DLC3010 on this page) converts the angle to 4–20 mA. Compared with other methods:
| Method | Principle | Suitable media | Limitations |
|---|---|---|---|
| Displacer | Displacer movement | Corrosive, hot, crystallizing media | Large displacer, not for small pipes |
| Conductive | Liquid conductivity | Water, conductive liquids | Not for non-conductive liquids |
| Capacitive | Dielectric constant change | Most liquids | Changing liquid composition interferes |
| Ultrasonic | Sound echo time | Non-foaming liquids | Foam and vapor interfere strongly |
| Radar | Microwave reflection | Many media (including hot) | High cost |
Choosing in practice: chemical tanks, semiconductor chemical tanks and petrochemical reactors with corrosive or crystallizing media often use displacer level; ordinary water tanks can use conductive or ultrasonic; avoid capacitive when media composition changes often. Products for other methods are available on request.
4–20 mA two-wire wiring, range selection and calibration
Wiring: the transmitter has only two wires, carrying both power and signal: 24 VDC positive → transmitter → signal receiver (PLC analog input card, typical 250 Ω load resistor) → back to 24 VDC negative.
Range: 1.5–2 times the actual operating value. For example, if you use up to 50 kPa, choose a 0–100 kPa range, not 0–500 kPa. At ±0.5% FS, absolute error grows with a large range, and accuracy becomes poor when the operating range is only a small part of the span.
Calibration: intervals are general cases and each still needs checking: 12–24 months for general industry, 6–12 months for critical chemical and semiconductor processes, and per SOP for GMP / FDA-regulated lines. Calibrate against a standard source (pressure calibrator, displacement calibrator), record five-point linearity (0%, 25%, 50%, 75%, 100% FS) and keep a calibration certificate on file.
The ranges, accuracies and calibration intervals here are general cases; each still needs checking. Confirm actual specs against the brand catalog and your process requirements.
How to request a quote: please send (1) the model (DLC3010 or DP transmitter); (2) the media, range and process connection; (3) the quantity; (4) how urgent it is.
Trademarks: Fisher, HART and the model names on this page are trademarks or model names of their owners, used here only to identify the parts. JIAHON is not the authorized distributor of Fisher in Taiwan.
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