SonTek/YSI Argonaut-XR Technical Manual - HydroScientific West

Using Frequency Pressure Sensors with SonTek/YSI Systems (June 2001)
SonTek/YSI Support Documentation
6837 Nancy Ridge Dr., Suite A • San Diego, CA 92121 • Telephone (858) 546-8327 • Fax (858) 546-8150 • Internet: support@sontek.com
Using Frequency Pressure Sensors with
SonTek/YSI ADPs, Hydras, and Argonauts
This document describes the use of frequency pressure sensors with SonTek acoustic Doppler
current meters. SonTek supports two types of frequency pressure sensors: (1) the Druck RPT, a
silicon resonant transducer (referred to as DRUCK) manufactured by Druck, Inc. and (2) the Paroscientific
digiquartz transducer (referred to as PAROSFREQ) manufactured by Paroscientific, Inc.
1. Overview
Typically, SonTek instruments include analog pressure sensors (e.g., strain gage) that provide
sufficient accuracy and stability (0.1 to 0.25 %) at a moderate cost. These sensors are usually installed
within the system head (Figure 1). They are internal to the system and are usually referred
to as PRESSURE or PRESSURE SENSOR within our documents and system command interface.
Some applications, however, require better long-term stability (e.g., tide studies, wave interaction
with topography, long-term water-level monitoring, etc.). To accommodate these needs, SonTek
has integrated frequency pressure sensors, which offer an order of magnitude better accuracy and
stability (0.01%). The first supported sensor was the Paroscientific digiquartz with a serial interface
(PAROS). These sensors, because of their size did not fit inside our systems and were
mounted externally (Figure 1). The next supported sensor, the Druck RPT, did fit inside an ADP
or ADVOcean head. However, for historical purposes, all non-strain gage sensors are usually referred
to as EXTERNAL PRESSURE SENSOR within our documents and system command interface.
2. Serial External Pressure Sensors (PAROS)
As mentioned, the first external pressure sensor supported by SonTek was the Paroscientific digiquartz
with serial interface (PAROS). The PAROS is connected to a system by a 1 to 2-m cable.
The PAROS is available for ADP, PC-ADP, and Hydra systems. The differences, when compared
with a strain-gage sensor, are as follows:
• The PAROS is an absolute sensor. It reads 1 dbar in air; a strain gage reports 0 dbars in air.
• Sampling rate is limited to 4 Hz (ADVs and Hydras) due to serial interface limitations.
Internal pressure sensor
(strain-gage or Druck RPT)
External Paroscientific
Pressure Sensor
Power and
communication cable
External Paroscientific
Pressure Sensor
Internal pressure sensor
(strain gage or Druck RPT)
SonTek ADP
Power and
communication cable SonTek ADVO
Figure 1: ADP and ADVOcean with external pressure sensors.
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