Improved Accuracy and Enhanced Reliability
The ZLS Dynamic Gravity Meter
The ZLS system digitizes input signals 200 times per second. All processing, including filtering, is done digitally. All control-loop algorithms, for both the platform and gravity sensor are performed digitally by an embedded computer, thereby eliminating analog circuits which enhances reliability and simplifies servicing.
The UltraSys™ utilizes an embedded processor to perform all the platform and sensor control functions. The power module may be located anywhere within 3 meters of the platform. A host computer, connected to the control module with a serial cable, completes the system. The embedded processor is connected to a host computer through a serial port. Using the ZLS-supplied software, the host computer processes the data as required for high resolution or standard marine operations and archives the final data. Raw data from the accelerometers, gyros and gravity transducers are digitized 200 times per second with a 16-bit A/D converter and then processed by the embedded computer. Analog signal outputs to control the motor and gyros are provided by a 16-bit D/A converter, which is also updated at 200 Hz. Slightly filtered data are transmitted to the host computer once per second.
The host computer stores all data on a hard disk and can simultaneously direct data to the video monitor, serial port and printer in a variety of formats. Either a numerical or graphical format may be selected for display on the printer. In high-resolution marine and airplane modes, raw data is recorded once per second, allowing the user to custom filter the data for specific applications. In marine mode, the data is filtered in an appropriate manner for marine data and recorded in 10-second intervals.
Additional external data may also be appended to the gravity data. The system accommodates up to four analog channels as well as a 24-bit digital channel. The system is fully automatic and will start unattended after a power interruption. Operation is as simple as turning on the switch and all system functions can be manually controlled through menu selections. All keystrokes are logged in a separate file for a complete record of system activity and system functions are continuously monitored. The UltraSys™ will automatically shut down in the event of a serious malfunction.
Type: Metal Zero-Length Spring
Hardened metal micrometer screw
Range: Standard: Worldwide 7,000 mGal Marine
Temperature range: -15 to +50 C
Drift: 3 mGals or less per month after aging
Static Repeatability: <0.1 mGal
Pitch: +/- 25 degrees
Roll:+/- 30 degrees
Period: Standard 4 minute, Optional 16 minute
Damping: 0.707 of critical
Power Requirements: 87 to 270 Vac 47 to 63 Hz single phase
Power Consumption: Operation: 1 A*, Maximum: 2.5 A*
* measured at 117 Volts 60 Hz.
Resolution of Recorded Data: 0.01 mGal
Clock and Gyro Power Source: Frequency: 200Hz
Temperature stability: 5 ppm -20C < T < +70C
Short term aging: 1 X 10-9/sec
Adjustability: sufficient for 5 years of aging.
Digital: 24 bit TTL compatible input
Analog: 4 channels, 16 bit resolution, Gains of 1, 2, 4, or 8 may be selected by menu
Sample rate 200 Hz