Test definitions for the evaluation of digital waveform recorders.

Abstract

This Test Definition for the Evaluation of Digitizing Waveform Recorders (DWR) defines the process that can be performed as part of the evaluation and testing of geophysical sensors, digitizers, sensor subsystems and geophysical station/array systems. DWR TEST DEFINITIONS General DWR Tests Static Performance Tests Static tests provide a constant or non time-varying stimulus to the DWR under evaluation. The purpose of these tests is to determine specific parameters such as: gain (accuracy at nominal, full-scale and overscale), DC offset, short-term and long-term stability, relationship to quantizing noise floor, and correlated/uncorrelated spurious signals. The results of these tests include measurement of dynamic range and resolution. DC Accuracy, Nominal (DWR-DCA) Purpose: The purpose of the DC accuracy test is to determine and verify the accuracy of the DWR. The bit-weight (LSB) of a non-gain-ranged digitizer is its resolution. Configuration: The DWR inputs are connected to a +/-DC voltage source, usually set to +/-1 volt. Evaluation: The DC gain (accuracy) of the DWR, DC offset, bit-weight (LSB)/resolution and counts/volt are measured. DC Accuracy, Full-Scale (DWR-DCFS) Purpose: The purpose of the DC full-scale test is to determine and verify the accuracy of the DWR at full-scale. The full-scale value is used in calculating Maximum Potential Dynamic Range (MPDR). Configuration: The DWR inputs are connected to a +/-DC voltage source set to the manufacturers specification for full-scale. Evaluation: The DC gain (accuracy) of the DWR, DC offset, bit-weight (LSB)/resolution and counts/volt at full-scale are measured. DC Accuracy, Over-Scale (DWR-DCOS) Purpose: The purpose of the DC over-scale test is to determine and verify the accuracy of the DWR at a specified value over full-scale. Configuration: The DWR inputs are connected to a +/-DC voltage source set to the manufacturers specification for over-scale. Evaluation: The DC gain (accuracy) of the DWR, DC offset, bit-weight (LSB)/resolution and counts/volt at over-scale are measured. AC Clip (DWR-ACC) Purpose: The purpose of the AC clip test is to determine and verify the maximum signal or clip level of the DWR. Configuration: The DWR input is connected to an AC voltage source set to 1 Hertz. The amplitude of the sinusoid is increased until the value of hard clip is reached. Evaluation: The AC clip voltage is measured. Input Terminated Noise (DWR-ITN) rate verification, the response of the DWR to UTC loss and power cycling, and the short-term stability of the DWR time base. Time-Tag Accuracy (DWR-TTA) Purpose: The purpose of the time-tag accuracy test is to verify the ability of the DWR to accurately time-tag the data samples with respect to the DWR inputs. Configuration: The DWR inputs are connected to a 1 Pulse per Minute (PPM) or 1 Pulse Per Hour (PPH) output of an independent running GPS Timing Reference. Evaluation: The time-tags of the data from the DWR are analyzed for correct time on the hour and minute transitions. DWR sample rate (samples per second/min...

Evaluation of Two Guralp Preamplifiers for GS21 Seismometer Application.

“…The tests that were conducted on the Guralp Systems GS21 Preamplifier were based on digitizer tests described in the test plan: Test Definition and Test Procedures for the Evaluation of Digitizing Waveform Recorders (Kromer, 2007).…”