Pressure transmitter vs differential pressure transmitter
First, the principle
We first clarify the principle of the pressure transmitter and differential pressure transmitter.
1, pressure transmitter principle
The electrical components that the pressure transmitter feels pressure are generally resistance strain gauges, which are sensitive devices that convert the pressure on the device under test into an electrical signal. The most widely used resistance strain gauges are metal resistance strain gauges and semiconductor strain gauges. The metal resistance strain gauge has two kinds of filament strain gauges and metal foil strain gauges. Usually, the strain gauge is tightly bonded to the mechanical strain matrix by a special adhesive. When the stress changes due to the force of the substrate, the strain gauges are also deformed together, so that the resistance of the strain gauge changes, thereby adding The voltage across the resistor changes.
2, differential pressure transmitter principle
The result measured by the differential pressure transmitter is the pressure difference, ie ΔP = ρg Δh. Since the oil tank is often cylindrical, the area S of the cross-section circle is constant, then the gravity G=ΔP·S=ρgΔh·S, S is constant, and G is inversely proportional to ΔP. That is, as long as the ΔP value is accurately detected, it is inversely proportional to the liquid level height h, and is proportional to the height difference Δh. When the temperature changes, although the oil volume expands or contracts, the actual liquid level rises or falls, and the detected The pressure is always the same.
Second, the characteristics
Pressure transmitter features
1. The pressure transmitter has the characteristics of reliable operation and stable performance;
2, dedicated V / I integrated circuit, fewer peripheral devices, high reliability, simple and easy to maintain, small size, light weight, installation and commissioning is extremely convenient;
3, aluminum alloy die-casting shell, three-terminal isolation, electrostatic spray protection layer, durable;
4, 4-20mA DC two-wire system signal transmission, strong anti-interference ability, long transmission distance;
5, LED, LCD, pointer three indicator head, the field reading is very convenient. Can be used to measure viscous, crystalline and corrosive media;
6, high accuracy, high stability. In addition to the original imported sensor has been corrected by laser, the comprehensive temperature drift and nonlinearity of the whole machine in the operating temperature range are finely compensated.
Differential pressure transmitter features
1. Measurement characteristics for pressure, differential pressure, liquid level, flow measurement
2, the numerical accuracy: + (-) 0.05%
3. Simulation accuracy: +(-)0.75%+(-)0.1%F.S
4, full performance: + (-) 0.25F.S
5, stability: 0.25% 60 months
6, range ratio: 100:1
7, measurement rate: 0.2S
8, miniaturized (2.4kg) all stainless steel flange, easy to install
9. Process connection is compatible with other products for optimal measurement
10, smart transmitter with 16-bit computer
11, standard 4-20mA DC, with digital signal based on HART protocol, remote control
12. Support upgrade to fieldbus and field-based technology
Third, the distinction
Through the principle and characteristics, we can clearly see that there is still a distinction between them. The pressure transmitter measures the pressure inside the pipe, and the differential pressure transmitter is the differential pressure corresponding to the orifice flowmeter. So we look at the transmitter to be divided into two, can not simply say that the transmitter is omnipotent, can measure all pressure, differential pressure.