Manganin pressure gauge

The experimental methods for the determination of the detonation wave parameters can be classified into two groups. The first, the so-called internal methods group, includes the methods by which detonation parameters are directly determined. These are the determination of the mass velocity of the detonation products by the electromagnetic particle velocity gauge method, direct determination of the detonation pressure by a manganin pressure gauge, determination of the mass velocity of the detonation products by the flash X-ray technique, etc. The time resolution of these methods can be on a nanoseconds scale, which is still not sufficient for fully reliable study of a very narrow chemical reactions zone, and in particular, of a shock wave front. 

Determination of the Detonation Pressure Using a Manganin Pressure Gauge... 

The principle of the determination of the detonation pressure by a manganin pressure gauge is based on the fact that under dynamic action of detonation pressure the electrical resistance of the gauge is changed. The resistance change is directly related to the measured detonation pressure. 

Table 4.1. Characteristics of some manganin pressure gauges...

Figure 4.60. Test charge assembly for determination of the d onation pressure by manganin pressure gauge...

The manganin pressure gauge is supplied by a constant voltage source that gives a rectangular voltage pulse. The pulse has an amplituduration time of 100 ps, and a current of 3-30 A. 

Power supply and measurement of the change of the manganin pressure gauge resistance, induced by the detonation wave action, are realised via a modified Wheatstone bridge circuit (Figure 4.62), ich, also enables calibration of the measuring system. 

The direct determination of the shock wave pressure in solids is based on registering the effects of dynamic action of the pressure on a specific property of some materials that are used as an active element in pressure gauges. Such gauges are, for example, the manganin pressure gauge and the carbon-resistant pressure gauge. 

The operating principle of the manganin pressure gauge is based on the change of the gauge resistance under the (fynamic action of pressure (see Subsection 4.2.6). The measured pressure is obtained from the calibrating diagrams. 

The manganin pressure gauges as well as the complete measuring equipment used for the determination of the detonation pressure are identical to that used for the shock wave pressure measurement (see Figure 4.61). 

The manganin pressure gauge is placed into the material where shock wave pressure is to be measured, as illustrated in Figure 5.29. 

Manganin pressure foil gauges began to be used for the determination of the detonation and shock wave pressure in the 1960s. Manganin, an alloy of copper, manganese, nickel, iron, and silica, is characterised by a significant... 

Song, S.-Y., and Lee, J.W. A Detonation Pressure Measurement System Employing High Resistance Manganin Foil Gauge, 9th Symposium (Inter-national) on Detonation, Portland, OR, 1989, pp. 226-232. 

Fig 23 Typical Pressure—Time Profiles from Multiple Embedded Manganin-Gauge Experiments. Labels indicate gauge distances from the impact face... 

Figure 10. Manganin gauge for pressure-time profiles [10]. (a) Bridge gauge layout (b) gauge assembly (c) record.

The manganin gauge may be calibrated by using a gas gun with known output characteristics, and a typical gauge coefficient foruid by the method is 0.0024 Q/Q/kbar. If only peak pressure is of interest, this may be determined by using an aquarium apparatus to determine the shock velocity produced in a material whose shock Hugoniot is known (in this case water) [21]. Because ofextrapola-... 

It is only recently that measurements have been made of the detonation pressure of lead azide, and similar data are not known for other azides. The values in Table VI were obtained using the manganin gauges described earlier, and the detonation velocities were obtained by streak photography [11]. 

X 10 " Pa is sufficient for accurate pressure measurements, and calibrated manganin gauges are commercially available. However, the precise value of the pressure coefficient depends not only on the composition of the alloy but also on its aging, and, in addition, the stresses which arise in the preparation of a resistor coil also effect the actual resistance. Therefore, special care seems to be necessary when one wants to obtain very good reproducibility with manganin gauges over extended periods of time. ... 

Figure 4.61. Schematic of measuring system for the determination of detonation pressure with a manganin gauge...

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