DENSE MEDIUM CONTROL | SUMP LEVEL
Differential Pressure Level Transmitter
Hydrostatic level measurement for the correct medium and dilute medium sumps. A 316 stainless steel diaphragm with silicone fill, no mechanical moving parts, and explosion-proof construction, reading level from pressure instead of from the surface.
±0.1%
Digital Accuracy
±0.25%
Analogue Accuracy
±0.5% (to 1.5 kPa)
Micro Range Accuracy
316 SS, silicone fill
Diaphragm
DEFINITION & OVERVIEW
What is a Differential Pressure Level Transmitter?
A differential pressure level transmitter measures level from pressure, not from the surface. Its diaphragm senses the hydrostatic head of the liquid above it, and that head rises and falls in direct proportion to level. Because nothing depends on a clear view of the surface, foam, agitation and a dusty or vapor-filled space above the sump do not disturb the reading.
In a dense medium circuit, this instrument watches the correct medium and dilute medium sumps. Those levels feed medium make-up and dilution decisions, so a level reading that drifts or drops out has a direct effect on cut-point control. It is one of the four instruments in our Dense Medium Control System, alongside density, magnetite content and pressure measurement.
John Finlay's unit holds ±0.1% accuracy on the digital signal and ±0.25% on the analog signal, with a micro range for differentials up to 1.5 kPa at ±0.5%. The diaphragm is 316 stainless steel with silicone fill, and the construction is explosion-proof with no mechanical moving parts. Zero and external connection are adjustable, with a 1:1 range ratio.
Reads Level from Pressure
Hydrostatic head across a diaphragm gives level directly, so foam, agitation or dust above the sump does not disturb the reading.
No Moving Parts
A 316 stainless steel diaphragm with silicone fill and no mechanical moving parts, in explosion-proof construction.
Shared Platform
Uses the same electronics platform and spare holding as the pressure transmitters in the system: one calibration procedure, one set of spares.
Parameter | Value |
|---|---|
Measuring Principle | Differential pressure (hydrostatic head) across a diaphragm |
Digital Signal Accuracy | ±0.1% |
Analogue Accuracy | ±0.25% |
Micro Range (up to 1.5 kPa) Accuracy | ±0.5% |
Static Pressure Effect | ±0.2% per 6.9 MPa, up to 13.7 MPa |
Span Error | ±0.25% per 6.9 MPa |
Zero and External Connection | Adjustable; range ratio 1:1 |
Diaphragm | 316 stainless steel, silicone fill |
Construction | No mechanical moving parts; explosion-proof |
KEY FEATURES
Key Features & Performance Highlights
Differential Pressure Level Transmitter
Accuracy Stated for Real Operating Conditions
Beyond the headline accuracy, the static pressure effect (±0.2% per 6.9 MPa up to 13.7 MPa) and the span error (±0.25% per 6.9 MPa) are published, so a specifying engineer can work out performance at line pressure instead of guessing.
Micro Range for Low Differentials
A micro range for differentials up to 1.5 kPa holds ±0.5%, suited to shallow sumps and low-head duty where a standard range would have little signal to work with.
No Moving Parts, Explosion-Proof Construction
Diaphragm sensing with silicone fill leaves nothing mechanical to wear, stick or foul in an abrasive medium sump, and the explosion-proof construction is built for demanding plant areas.
WORKING PRINCIPLE
How the Differential Pressure Level Transmitter Works
Level is read from the weight of the liquid above the diaphragm, not from the surface.
Diaphragm in the Sump Line
The 316 stainless steel diaphragm, silicone-filled, is exposed to the pressure of the medium at the sump.
Hydrostatic Head Sensing
The pressure at the diaphragm rises and falls with the height of the medium above it, so the differential pressure is a direct measure of level.
Zero and Range Set
Zero and external connection are adjustable, with a 1:1 range ratio.
Signal Conversion
The sensed differential pressure is converted to a calibrated level signal at ±0.1% (digital) or ±0.25% (analogue) accuracy.
Into the Control Scheme
The level signal joins density, magnetite concentration and pressure in the Dense Medium Control System, informing medium make-up and dilution decisions.
TECHNICAL SPECIFICATIONS
Differential Pressure Level Transmitter | Full Specification
Parameter | Value |
|---|---|
Digital Signal Accuracy | ±0.1% |
Analogue Accuracy | ±0.25% |
Micro Range (up to 1.5 kPa) Accuracy | ±0.5% |
Static Pressure Effect | ±0.2% per 6.9 MPa, up to 13.7 MPa |
Span Error | ±0.25% per 6.9 MPa |
Zero and External Connection | Adjustable |
Range Ratio | 1:1 |
Diaphragm | 316 stainless steel, silicone fill |
Construction | No mechanical moving parts; explosion-proof |
COMPARISON
Differential Pressure vs. Insertion Tuning-Fork Concentration Measurement
Differential Pressure Level Transmitter
Radar and Ultrasonic Level (Non-Contact)
Applications of the Differential Pressure Level Transmitter
Anywhere a dense medium circuit needs a steady, continuous sump level signal.
Correct Medium Sump Level
Tracks the level of the correct medium sump, a key input to medium make-up.
Dilute Medium Sump Level
Tracks the dilute medium sump level, supporting dilution and medium balance.
Pump Protection and Overflow Alarms
A continuous sump level signal supports low-level pump protection and high-level overflow alarms.
Low-Head and Shallow Sumps
The micro range for differentials up to 1.5 kPa, at ±0.5%, covers low-head duty.
Closed-Loop Medium Management
Feeds the control scheme of the Dense Medium Control System alongside density, magnetite concentration and pressure.
About John Finlay
Level Instrumentation Supplier in India
Why John Finlay?
±0.1%
Digital Signal Accuracy
Published alongside static pressure effect and span error, so performance at line pressure can be worked out.
130+
Coal Washery Projects
Completed EPC projects worldwide, including Asia’s largest coking coal washery at 30 MTPA.
EPC
Full Circuit Supply
Supplied as part of a complete instrumentation and automation offering across the coal preparation flowsheet.
IN
India-Based Support
Manufactured at Hefei John Finlay Mining Equipment Co., Ltd. and supported locally in India for installation, commissioning, spares and service.
Differential Pressure Level Transmitter | Frequently Asked Questions
Common questions from coal washery process engineers choosing sump level measurement.
A diaphragm senses the hydrostatic pressure of the medium above it. That pressure rises and falls in direct proportion to level, so the transmitter converts it to a level signal. It does not need to see the surface.
On the correct medium and dilute medium sumps. Those levels inform medium make-up and dilution, so they matter to cut-point control.
Yes. Hydrostatic level depends on the density of the liquid above the diaphragm, so it suits sumps where density is held near a set point, as it is in a controlled dense medium circuit. Where density swings widely, talk to our engineers about how that affects your sump level reading.
±0.1% on the digital signal and ±0.25% on the analogue signal, with a micro range for differentials up to 1.5 kPa at ±0.5%. The static pressure effect and span error are published in the specification.
Radar and ultrasonic read the surface, which suits tall silos and bunkers. In a sump with foam, agitation or a dusty space above the liquid, a hydrostatic reading is steadier. For the non-contact options see our Radar Level Transmitter and Ultrasonic Level Transmitter.
Yes. The level and pressure transmitters share a common electronics platform and spares holding, so one calibration procedure and one set of spares covers both.
Need a steadier sump level reading in your dense medium circuit?
Our engineers can help you choose the right level measurement for each sump.
Talk to an ExpertRelated Equipment
Radar Level Transmitter
Non-contact level up to 120 m, for silos and bunkers.
Ultrasonic Level Transmitter
Non-contact level up to 15 m with no commissioning steps.
Dense Medium Control System (S1)
The packaged system this transmitter is part of.
Differential Pressure Density Meter
The density instrument on the same correct and dilute medium lines.