Guralp Systems Limited
MAN-D24-0004 - Güralp DM24 MkⅢ Operator's Guide

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1. Preliminary Notes 2. Introduction 3. Installing the DM24 4. Using the DM24 5. Using Scream! 6. Command line interface 7. Inside the DM24 8. Güralp Compressed Format 9. Connector pin-outs 10. Digitiser specifications 11. Revision history

Chapter 10. Digitiser specifications

Seismic channels

Number

4 – 8

Format

32 bit

Inputs

Differential with transient protection; ±10 V input range

Input impedance

1 MΩ, 10 nF

Common mode rejection ratio

110 dB at 10 Hz

Mux channels

Number and Format

Eight 24-bit channels

Inputs

Single ended; ±10 V input range

GPS

Unit

External GPS (CMG­GPS2)

Power

supplied through GPS connector

Time format

NMEA

Max. cable length

50 m

Sensor control

Functions available

Lock, unlock and centre sensor (active low CMOS); enable calibration

Sensor calibration

Types

Sine and square wave; adjustable amplitude and frequency

Digital signal processing

Type

Texas TMS320CV33

Hardware sampling rate

2 KHz

Sample output rates

6 cascaded rates, each 2, 4, or 5 times lower than the previous rate

Anti-aliasing filters

2 pole

Low-pass filters

FIR

Out-of-band rejection

140 dB

In-band ripple

–140 dB

Trigger modes

STA/LTA, threshold, external trigger

Digitiser performance

Output format

32 bit

Noise-free resolution (NPR)

22.5 bits at 20 samples/s; 21.5 bits at 100 samples/s

Absolute accuracy

0.5% standard (0.1% optional)

Type

5th-order, single-bit, low-pass noise shaper

Clock

Oscillator

8 × 10–7 standard (5 × 10–8 oven-controlled optional)

External receiver interface

GPS or GLONASS: RS232 and PPS

External receiver synchronisation

<50 µs

Internal thermometer

Accuracy

±0.33 °C (30 °C)
±0.5 °C (10..50 °C)
±1.0 °C (–10..75 °C)

Linearity

±0.5 °C

Resolution

0.0625 °C

Power 

Supply

+10 to +24 V DC

Current at 12 V DC

~0.12 A

PreviousNext

1. Preliminary Notes 2. Introduction 3. Installing the DM24 4. Using the DM24 5. Using Scream! 6. Command line interface 7. Inside the DM24 8. Güralp Compressed Format 9. Connector pin-outs 10. Digitiser specifications 11. Revision history