Extended Diaphragm Seal DP Level Transmitter

Extended Diaphragm Seal DP Transmitter is a level transmitter direct mounted on pipe or tank. The isolation diaphragm is in direct contact with the liquid medium.

Extended Diaphragm Seal DP Level Transmitter

Extended Diaphragm Seal DP Level Transmitter is a field level transmitter that is directly mounted on a pipe or container. The isolation diaphragm is in direct contact with the liquid medium. There is no need to lead out the positive pressure side with a pressure pipe. Therefore, it can measure the liquid level, pressure and density of high temperature, high viscosity, easy crystallization, easy precipitation and strong corrosion. Convert to 4 ~ 20mA. DC signal output.

The flanges are made of high-quality stainless steel materials such as 304 and 316. Wetted diaphragms are made of imported high-quality anti-corrosive materials such as 316L, Hastelloy C-276, Monel, and tantalum.

Sino-Inst offers a variety of DP pressure transmitters for industrial pressure measurement. Connection with diaphragm seals. If you have any questions, please contact our sales engineers.

Features of Extended Diaphragm Seal Differential Pressure Transmitter

  • Simple structure: There are no movable or elastic elements. Therefore, the reliability is extremely high. The amount of maintenance is very small.
  • Easy installation: The built-in structure especially shows this feature. No special tools are required.
  • Convenient adjustment: The two potentiometers of zero position and range can carry out zero point migration or range change at will within the effective range of liquid level detection. The two adjustments do not affect each other.
  • Widely used: Suitable for liquid level measurement of high temperature and high pressure, strong corrosion and other media.

Specifications of Extended Diaphragm Seal Level Transmitter

Measuring range:can be customized within the range of -4-4MPa (-10-10KPa, 0-50KPa, etc.)
Output signal: 4 ~ 20MA.DC two-wire system (analog). Two-wire system 4 ~ 20mA DC signal is superimposed with digital signal. Linear or square root output is selected by the user. (Smart)
Power supply:12 ~ 45V.DC
Range ratio: 10: 1 or 100 to 1
Power supply impact: <0.005% output range / V
Load effect: When the power supply is stable, there is no load effect.
Measurement accuracy: 0.1% of the calibration range. Standard accuracy is 0.2%. If other accuracy is selected, please indicate when ordering and selecting.
Resistance: usually adjustable between 0.1 to 16 seconds. When filling with inert liquid or with a remote transmission device, the time constant will increase.
Startup time: <2 seconds, no warm-up required
Working environment: ambient temperature -29 ~ 93 ℃ (analog amplifier)
 -29 ~ 75 ℃ (digital / smart amplifier)
    -29 ~ 65 ℃ (with display head)
Environmental humidity: 0 ~ 95%
Protection characteristics: protection ability IP65
Explosion-proof type: Flameproof Exd II BT4-6. Intrinsically safe Exia II CT5
Static pressure effect:Zero point error (can be eliminated under static pressure)
Static pressure from 0 ~ 13.7MPa, ± 0.2% / 6.9MPa
 Static pressure exceeds 13.7MPa, ± 0.5% / 6.9MPa

Extended reading: Smart Differential Pressure Transmitter

Applications of Extended Diaphragm Seal DP Level Transmitter

Extended Diaphragm Seal DP Transmitter can measure the liquid level, pressure and density of high temperature, high viscosity, easy crystallization, easy precipitation and strong corrosion and other media. Then convert it to 4-20mA. DC signal output

Mainly used for measurement in the following occasions:

  • Viscous medium at high temperature.
  • Easily crystallized medium.
  • Precipitated media with solid particles or suspended matter.
  • Strongly corrosive or highly toxic media.
  • It can eliminate the leakage of the pressure guiding pipe and pollute the surrounding environment. When the isolation liquid is used, the tedious work of frequently replenishing the isolation liquid due to the unstable measurement signal can be avoided.
  • Continuously and accurately measure the interface and density.
  • The remote transmission device can avoid the mixing of different instantaneous media, so that the measurement results truly reflect the actual situation of process changes.
  • Hygiene and cleaning requirements are high.
  • For example, in the production of food, beverage and pharmaceutical industries, not only the location of the transmitter in contact with the media must meet hygienic standards, but it should be easy to rinse.

You may like: Diaphragm pressure gauge

Extended Diaphragm Deal Application

Diaphragm seals are used for the protection of pressure measuring instruments in applications with difficult media. In diaphragm seal systems, the diaphragm of the diaphragm seal affects the separation of the instrument and the medium.

The pressure is transmitted to the measuring instrument via the system fill fluid which is inside the diaphragm seal system.

For the implementation of demanding customer applications, there are a wide variety of designs, materials and system fill fluids available.


  • Aggressive, highly viscous, crystallising or hot media
  • Process industry
  • Thick-walled or insulated pipelines and vessels

Read more What is a diaphragm seal?

1199EFW Extended Diaphragm Seal

The specifications of commonly used Extended Diaphragm Seals are as follows:

DN50 (2 ”) flange size specification table

FlangeACFEBNumber of bolts nBolt diameter

DN80 (3 ”) flange size specification table

FlangeACFEBNumber of bolts nBolt diameter

DN100 (4 ”) flange size specification table

FlangeACFEBNumber of bolts nBolt diameter

Rosemount 1199 remote transmission diaphragm system provides the world’s most extensive product variety and specifications to meet the requirements of various measurements and applications.

There are the following types of remote transmission differential pressure / level transmitters:
1) PFW flat type remote transmission device
2) RTW thread installation type remote transmission device
3) EFW inserted barrel remote transmission device
4) RFW flange mounted remote transmission device
5) SCW hygienic remote transmission device

The 1199 remote diaphragm can be assembled to Sino-Inst differential, gauge and absolute pressure transmitters and liquid level transmitters.

Extended reading: SI-703 Flush Diaphragm Pressure Sensor

Diaphragm type level transmitter working principle

Smart differential pressure transmitters are often used to measure liquid level, flow rate, etc. Differential pressure transmitter cooperates with sealing diaphragm, capillary, etc.

The differential pressure type liquid level gauge uses the principle that when the liquid level in the container changes, the static pressure generated by the liquid column also changes accordingly, as shown in the figure.

For closed tanks. Set the bottom pressure to P. If the pressure on the liquid surface is P3 and the liquid level height is H, then:

P = P3 + Hpg (3-11)

In the formula: p is the medium density; g is the acceleration of gravity.
From the formula ((3-1 “available:
△ P = P-P3 = Hpg (3-12)

Usually the density of the measured medium is known, the pressure difference △ P is proportional to the liquid level height H. The pressure difference on the side will know the measured liquid level height.

When the container under test is open, the gas pressure is atmospheric pressure. The negative pressure chamber of the differential pressure gauge can be vented to the atmosphere. It is known that the pressure gauge can also be used to measure the liquid level at this time. If the container is closed, you need to connect the negative pressure chamber of the differential pressure gauge to the gas phase of the container.

Pressure level transmitter is good for level measurement. Most of the time, we use submersible hydrostatic level sensor for the level measurement. When you can not use the probe of hydrostatic level sensor, you can try with this pressure level transmitter. Pressure level transmitter, is one type of DP level measure instrument, with the diaphragm.


SMT3151LT Differential pressure (DP) level transmitter a new type of differential pressure (DP) transmitter produced by advanced technology and equipment. Continuous level, flow and differential pressure measurement. Liquid level measurement, is the most common measurement process in continuous production processes, such as: petroleum and chemical industry. The liquid level measuring instrument currently widely used, is the differential pressure level transmitter.


SMT3151DP intelligent differential pressure transmitter uses advanced microprocessor technology and digital communication technology. The basic principle of differential pressure transmitter is: divide a space with sensitive elements (multi-purpose capsule) into two chambers. Introduce pressure into the two chambers separately. The sensor produces displacement (or displacement trend) under the combined action of the two pressures. This displacement is proportional to the pressure difference (differential pressure) between the two chambers. Convert this displacement into a standard signal output that can reflect the magnitude of the differential pressure.

Comparative analysis – 7 Tank Level Measurement Sensors

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This entry was posted in Pressure, Diaphragm Seal, DP Transmitters by KimGuo11. Bookmark the permalink.

About KimGuo11

Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects. Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.