Built-in servo type accelerometer seismic monitoring system (SW-72 / SW-72R)

Highly accurate compact seismometer built with sensor
Adopting high accuracy servo type accelerometer. SW-72R is high-end model which accepts measurement of SI value and seismic intensity.
Seismic Monitoring System<SW-72>


  • ■ Reliable accuracy
    Reliable accuracyBuilt - in servo type accelerometer is also used for detection of micro-tremor. Both indication setting and alarm setting is 1 gal step.
  • ■ Waterproof structure
    Waterproof structureIt is ideal to install the seismometer on the common foundation to catch the motion of earthquake correctly. SW-72/72R adopts waterproof structure equivalent to IP67’s which is able to be installed outside or dusty environments.
  • ■ Available to large-scale earthquake monitoring
    The peak of motion in any direction can be surely captured by vector composition of the accelerations detected by the accelerometers arranged in three directions. The measurable acceleration range up to 5000 gal prepare against the large-scale earthquake.
    Available to large-scale earthquake monitoring
  • ■ Easy installation
    Easy installationFor the conventional seismometers, 4 points are requested to be fixed by anchor bolts. SW-72 or SW-72R has two cut-out holes for fixing bolts so that bolt position adjustment can be easier.
  • ■ Compact design
    Compact designIn addition to the compact size, the cable port is located at the lower part and outer round shape to be surrond friendly.

System composition

System composition

Outward dimensions

  • Outward dimensions(SW-72)
  • Outward dimensions(SW-72R)


Item SW-72 SW-72R
Detecting method Omni-directional, non-directivity detection by vector composed acceleration
Built-in pickup Force-balance servo type accelerometer
Frequency range 0.3 to 10 Hz ±10 %
0 to 5000 gal (3–component vector product)
NS / EW direction : ± 3000 gal, UD direction : + 2000 to - 4000 gal
SI value
Measurement range - 0.1 to 1500 Kine (3-component vector product)
Period range 0.1 to 2.5 sec. ±10 % (natural period 0.1 sec. step, figured out 25 of 1-freedom simulation filters)
Damping Can be set by 1 % step
Low pass filter 30 Hz (-3 dB), 4th butterworth
A / D converter 16 bit, 100 Hz sampling
Display 7-segment LED, 4-digit display (xxx.x or xxxx)
Alarm Alarm step Upper limit 3-step (ALM1–3) individual setting Upper limit 3-step (ALM1–3) individual setting (acceleration / seismic intensity / SI value)
Alarm setting Level 0.1–999.9 gal *1 setting interval 0.1 step, 0.0 is alarm operation OFF 0.1 to 999.9 (gal / seismic intensity / Kine) 0.1step, alarm operation is OFF at 0.0
Alarm contact 1a contact (photo MOS relay, COM common)
Contact rating 200 V - 0.65 A (AC / DC peak value)
Relay Made by Panasonic PD1a type (AQY277A)
Alarm reset
a. Automatic reset by an internal timer 1–9999 sec. (setting interval : 1 sec., 0 is automatic reset OFF)
b. External reset terminals (all steps reset by no-voltage a contact)
DC output DC4 – 20 mA, load resistance < 300 Ω
Full scale : 10 to 3000 gal (setting interval : 1 gal)
DC4 – 20 mA, load resistance <300 Ω , output content switching type (acceleration/ SI value / seismic scale by internal setting)
Full scale value : settable optionally up to scale 7
Serial I/F Communication with SW-74 (conforms to RS422) / For maintenance (conforms to RS232C) Communication with SW-74SI(conforms to RS422) / For maintenance (conforms to RS232C)
Clock Accuracy < 70 ppm (daily error of 6 seconds)
Time calibration ±30 sec. correction (external input of no-voltage a contact)
Operational temperature range 0 to + 50 °C
Operational humidity range 10 to 100 %RH (non-condensing)
Power supply DC24 V ± 10 % less than 10 W *2 DC24 V ± 10 % less than 15 W *2
Structure Waterproof (equivalent to IP67)
Material Aluminum die-casting
Mass Approx. 1.5 kg
Mounting method Installation on the ground (fixed by anchor)
I / O cable Waterproof connector
One-touch lock connector (made by Nanaboshi Electric)
NRW-2421PF11 (connector diameter : approx. 34.1 mm)
Twisted cable with shielded (made by Fuji Electric Wire)
FKEV-SB 0.3sq×10 pair (outer diameter : approx. 10.5 mm)

*1 Initial setting values are 80, 250, 400 gal
*2 When connected with SW-74 (74SI) , power is supplied from SW-74 (74SI)