Instrumentation: [Weekly Question] Week 31 of 2011: Issues with the sensing elements of differential pressure transmitters.

This post was last edited by denghl on 2012-12-21 at 21:38. Reply to 1#: The diaphragm box in Baghdad can handle a unidirectional operating pressure, while the operating pressure of a differential pressure transmitter is often much higher than the differential pressure being measured; as a result, the measuring element is inevitably subjected to a unidirectional operating pressure that is far above its measurement range. A single-diaphragm design offers high sensitivity, but it cannot withstand one-way overloads; therefore, most differential pressure transmitters use diaphragm packs.

This post was last edited by denghl on 2012-12-21 at 21:40. Reply to 1# Baghdad: The sensing elements of differential pressure transmitters generally fall into two types: single-diaphragm and diaphragm-box assemblies. The single-diaphragm type is easy to manufacture and has high sensitivity, but it cannot withstand one-way overloads. The sensing element in the vast majority of differential pressure transmitters is a diaphragm box assembly. This is because such assemblies exhibit excellent sensitivity and linearity within the range of differential pressures for which they are designed to operate. Even when the differential pressure exceeds this operating range, that is, in the case of one-way overload, the diaphragm does not get damaged and its performance is hardly affected – this is a characteristic of the diaphragm box structure. Since the diaphragm box is filled with silicone oil, in addition to transmitting pressure it also provides damping, resulting in a stable instrument output.

This post was last edited by denghl on 2012-12-21 at 21:44. I’m not an expert in instrumentation; as far as I know, a diaphragm box design is used to facilitate the deformation of the diaphragm. A single-diaphragm design seems feasible as well, but its accuracy and service life will be affected!

This post was last edited by denghl on 2012-12-21 at 21:45. Since the diaphragm pack exhibits excellent sensitivity and linearity within the operating differential pressure range, it does not get damaged, nor does it suffer any significant effects even when the differential pressure exceeds this range, that is, in the case of one-way overload； Since the diaphragm box is filled with silicone oil, it not only transmits pressure but also provides damping, resulting in a stable output from the instrument ； It can be seen from the above that a single diaphragm cannot withstand one-way overload; although it is easy to manufacture and has high sensitivity, it is not suitable for use.

This post was last edited by denghl on 2012-12-21 at 21:47. 1. Within the operating differential pressure range, the diaphragm package exhibits good sensitivity and linearity; whereas when the differential pressure exceeds this range, that is, in the case of one-way overload, the diaphragm not only remains intact but also suffers little impact； 2. Since the diaphragm box is filled with silicone oil, in addition to transmitting pressure it also provides damping, resulting in a stable output from the instrument. A single diaphragm cannot withstand one-way overload; although it is easy to manufacture and highly sensitive, it is not suitable for use.

Let’s think about it; this is really a difficult question to answer

This post was last edited by denghl on 2012-12-21 at 21:48. Since the diaphragm pack exhibits excellent sensitivity and linearity within the operating differential pressure range, it does not get damaged, nor does it experience much impact even when the differential pressure exceeds this range, that is, in the case of one-way overload； Since the diaphragm box is filled with silicone oil, it not only transmits pressure but also provides damping, resulting in a stable output from the instrument ； It can be seen from the above that a single diaphragm cannot withstand one-way overload; although it is easy to manufacture and has high sensitivity, it is not suitable for use.

Since diaphragm boxes can withstand unidirectional operating pressures, the operating pressure of differential pressure transmitters is often much higher than the differential pressure being measured. Due to careless operation or other abnormal conditions, the measuring element may inevitably be subjected to unidirectional operating pressures that are far above its measurement range. Although a single diaphragm is easy to manufacture and highly sensitive, it cannot withstand unidirectional overloads; therefore, diaphragm boxes are used in the vast majority of differential pressure transmitters. At the same time, within the operating differential pressure range, the diaphragm box assembly exhibits good sensitivity and linearity; it is less affected when the differential pressure exceeds this range.

This post was last edited by denghl on 2012-12-21 at 21:50. Since diaphragm boxes can withstand unidirectional operating pressures, the operating pressure of differential pressure transmitters is often much higher than the differential pressure being measured. Due to careless operation or other abnormal conditions, the measuring element may inevitably be subjected to a unidirectional operating pressure that is far above its measurement range. Although a single diaphragm is easy to manufacture and highly sensitive, it cannot withstand unidirectional overloads; therefore, most differential pressure transmitters use diaphragm boxes. At the same time, within the operating differential pressure range, the diaphragm box assembly exhibits good sensitivity and linearity; it is less affected when the differential pressure exceeds this range.

This post was last edited by denghl on 2012-12-21 at 21:51. Since diaphragm boxes can withstand unidirectional operating pressures, the operating pressure of differential pressure transmitters is often much higher than the differential pressure being measured. Due to careless operation or other abnormal conditions, the measuring elements may inevitably be subjected to unidirectional operating pressures that are far above their measurement range. Although a single diaphragm is easy to manufacture and highly sensitive, it cannot withstand unidirectional overloads; therefore, most differential pressure transmitters use diaphragm boxes. At the same time, within the operating differential pressure range, the diaphragm box assembly exhibits good sensitivity and linearity; it is less affected when the differential pressure exceeds this range.