Quartz and Lithium Niobate Shock Gauges
X-cut quartz is one of the most accurate and reproducible materials for measuring short-duration, one-dimensional stress pulses. The Ktech gauges operate in the current mode and are configured with an internal shunted center electrode and guard ring. The electrical output is well characterized up to a maximum stress of 2.5GPa (25kbar). The response time of the gauges is less than 1 nanosecond and the useful "read-time" of the gauge is limited to one transit time through the thickness of the crystal which is typically 0.2-1.0 microseconds. Signal conditioning is not required, but high bandwidth cable and data acquisition systems are required for measuring full performance. All standard quartz gauges have internal 50-Ohm current viewing resistors (CVRs) and internally shunted guard rings. Guard ring widths are 1.5 times the crystal thickness. Standard output connectors are SMA-type. Gauge housing is 6061-T6 Aluminum.
Lithium niobate piezoelectric sensors are used in a manner similar to x-cut quartz for the measurement of short duration stress waves. Lithium niobate has a higher shock impedance than x-cut quartz and a higher sensitivity. Therefore, it provides some flexibility to the experiment designer when dealing with higher impedance materials and/or low amplitude limits are lower than than x-cut quartz.
Gauge Specifications
The Ktech model number KI-X-Y-Z defines the crystal diameter, X, the crystal thickness, Y, and the center electrode diameter, Z, KQ species on X cut quantity gauge, KL specifies a Z cut lithium niobate gauge.
Available crystal dimensions and the performance of each quantity gauge type are defined in Table 1.
All X-Cut Quartz crystals are manufactured to the Sandia National Laboratories Quartz Gauge Standard (SNL-DS-T04908), still under gauge specifications. Each crystal is inspected for internal flaws and achmites. Crystal dimensions are held to +/-0.001 in. diameter, +/- 0.0005 in thickness, and +/- 0.0005 in parallelism. The impact face is flat to within 3 wavelengths sodium light.
Lithium Niobate
Table 2 summarizes the capabilities of Lithium Niobate sensors and compares its response to x-cut quartz. Ktech Corporation manufactures Lithium Niobate gauges in the same configurations as x-cut quartz.
Table 2.
| x-cut quartz |
1.0 |
+4.8 |
1.04 |
4.0 |
| z-cut lithium niobate |
4.6 |
+2.5 |
1.08 |
0.8 to 1.4** |
| y-cut lithium niobate |
6.5 |
-1.3 |
1.51 |
1.8 |
| 36° rotated y-cut lithium niobate |
11.8 |
0 |
1.51 |
0.8 |
|
*Ratio of final current to initial current during transit of stress pulse with step function input.
**Different limiting stresses are observed depending on gauge thickness. The higher limits are characteristic of thicker gauges. |
Special Orders
Special orders, such as dimensional, electrical and material variations on the above transducer assemblies are welcome. Price quotations for special orders can be provided by contacting technical support.
