Please compare: what is the quality of capacitive differential pressure transmitters produced in our country at present?

Waiting online... Hope experts in this field can provide some answers!

This post was last edited by qugd on 2011-3-4 at 18:32. The EJA / EJX series no longer come with capacitive types; they are all of the monocrystalline silicon resonance type. The capacitive type you mentioned is a product from the last century; of course, it’s still being manufactured today. That’s because some people have a special fondness for older devices, or they are reluctant to spend money on better products. Capacitive types also have advantages, as they allow operators responsible for instrument maintenance to develop their skills in making on-site adjustments, thereby adapting to the variable characteristics of capacitive transmitters. Once you use a monocrystalline silicon or resonant silicon transmitter, such opportunities for training are essentially gone.

Hehe, it seems the person above has a deep understanding of differential pressure transmitters? I also did some searching, and it seems that the capacitive differential pressure sensors used by Rosemount are quite good at the moment EJA is indeed made of monocrystalline silicon; I was wrong! Could you please mention what the disadvantages of capacitive differential pressure sensors are? And what are the differences between domestic transmitters and them? My personal experience is that it’s easier to lose at zero? Is it necessary to calibrate the zero point frequently? I’m not sure if all domestic differential pressure transmitters have this problem

The unit is EJA; Rosemount also uses it. There’s nothing negative to say about that gauge – it’s tested using capacitive methods, has good sealing, and requires little maintenance. However, for less critical applications, we use those produced by Chongqing Weian in China! It was also tested using a capacitor; apart from the zero-point drift issue you mentioned, there are many other problems – poor sealing that leads to water ingress, and the electrical components inside have a rather rough construction! The water inlet can easily overheat, and it requires a lot of maintenance! Prone to damage! But it’s relatively cheap......

Oh, are the impressive drifts you encounter in Chongqing that big? I hope those who have personal experience will come and give some advice?

Reply to 6# cqcclt2004: It’s not the case that it drifts all the time… The worst incident I’ve experienced was when, after removing it in the morning and taking it to the calibration station for adjustment, its pressure started to drift by 4-5 KPA by the afternoon! There’s really no other choice; I have to go back to the factory for repairs!

Reply to 3# qugd: Haha, that’s a sharp reply. For transmitters, it’s better to spend a bit more money; those made in China are somewhat better, with Xiyi being a decent option. Our factory uses it well. Its stability is still inferior to that of the EJA

This post was last edited by zhwsyb on 2011-3-5 at 11:00. We are also an OEM manufacturer of transmitters. A few years ago, some intermediaries sold products to the Northeast region, and those products exhibited significant drift; however, the problem was resolved after we subjected the products to ultra-low-temperature drift testing prior to shipment. So it’s not that all domestic instruments are of poor quality; rather, the applicable operating environments are not properly understood. The main reasons for zero drift in pressure sensors are as follows: 1. Bubbles or impurities in the adhesive layer of the strain gauge; 2. Unstable performance of the strain gauge itself; 3. Poor solder joints in the circuit; 4. Incomplete stress release in the elastomer ； It is also related to many factors such as magnetic field, frequency, temperature, etc. Electrical drift or some form of drift will always be present, but we can reduce its extent or correct it through certain methods. Zero-point thermal drift is an important parameter affecting the performance of pressure sensors, and it receives considerable attention. Internationally, it is believed that zero-point thermal drift depends only on the non-uniformity of the force-sensitive resistor and its temperature non-linearity; in fact, zero-point thermal drift is also related to the reverse leakage current of the force-sensitive resistor. In this regard, polysilicon can remove heavy metal impurities from the substrate, thereby reducing the reverse leakage of force-sensitive resistors, improving zero-point thermal drift, and enhancing the performance of the sensors. What are other ways to reduce electrical drift and correct it? What other significant effects does zero-point electrical drift have, in addition to affecting the measurement accuracy of pressure sensors and reducing their sensitivity? Zero-point electrical drift can be utilized to eliminate the thermal zero-point drift of pressure sensors. Zero-point drift refers to the phenomenon in which an irregular, slowly varying voltage is generated at the input terminal when the input terminal of the amplifier is short-circuited. The main causes of zero-point drift are the effect of temperature changes on transistor parameters and fluctuations in supply voltage. In most amplifiers, zero-point drift has the greatest impact at the preceding stages; the more stages there are and the higher the gain, the more severe the zero-point drift becomes. The magnitude of drift mainly depends on the choice of strain material; the structure or composition of the material determines its stability or thermosensitivity. The processing of the materials after they have been selected is also very important; different manufacturing processes yield different strain values. The key lies in achieving stability in the bridge values or in regular changes in these values through adjustments such as aging. There are many ways to adjust drift, and these are mostly determined by the manufacturer’s conditions or production requirements; nowadays, most manufacturers are able to control zero-point drift quite well. Temperature regulation can be achieved through internal temperature resistors, heating zero-sensitivity resistors, compensation, aging, etc.

Try using Baxter’s version of the domestically produced one; I wonder where the original poster is from? Voltage transformer drift generally refers to zero drift and temperature drift; in some cases, there is no drift at high temperatures but drift occurs at low temperatures. Before placing an order, it is necessary to clarify working conditions such as ambient temperature with the supplier.

Hehe, a few kPa of fluctuation in one day is a bit much; I guess it’s broken now! Well, I usually use micro-differential pressure transmitters; their maximum range is no more than 8 kPa. Normally, the zero drift is around 30–50 Pa, which I consider to be quite high. Since I use these devices to measure flow rates, such a large drift in pressure means that the measurement errors will definitely be significant! What degree of drift do people consider to be within the normal range for micro-differential pressure transmitters? How much drift is typical for domestic differential pressure transmitters?