Campbell Scientific DB1 User Manual

DB1 Liquid Level

Measurement Sensor

Revision: 12/07

Copyright © 1993-2007

Campbell Scientific, Inc.

Warranty and Assistance

The DB1 LIQUID LEVEL MEASUREMENT SENSOR is warranted by
CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and
workmanship under normal use and service for twelve (12) months from date
of shipment unless specified otherwise. Batteries have no warranty.
CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to
repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective
products. The customer shall assume all costs of removing, reinstalling, and
shipping defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL
SCIENTIFIC, INC. will return such products by surface carrier prepaid. This
warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products
which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties,
expressed or implied, including warranties of merchantability or fitness for a
particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,
indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone [phone]. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.

RMA#_____
815 West 1800 North
Logan, Utah 84321-1784

CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

DB1 Table of Contents

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the Adobe Acrobat® bookmarks tab for links to specific sections.

1. Overview.......................................................................1

2. Specifications ..............................................................2

3. Installation....................................................................2

4. Wiring............................................................................3

5. Programming ...............................................................6

5.1 CR1000 Example......................................................................................6

5.2 CR10(X) Example....................................................................................7

6. Maintenance...............................................................10

6.1 Periodic Maintenance .............................................................................11

6.2 Solenoid Valve .......................................................................................11

6.3 Fittings.................................................................................................... 11

6.4 Needle Valve ..........................................................................................11

7. Replacement Parts ....................................................12

Figures

1 and 2. The DB1 System...............................................................................4

3. Wiring Diagram for DB1............................................................................5

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DB1 Liquid Level Measurement Sensor

1. Overview

The double bubbler is a self-calibrating system for liquid level measurement.
This manual focuses on water level measurement in stilling wells or open
channels, but the information applies to other liquids as well. The system
detects water level by measuring the pressure required to force a nitrogen gas
bubble from a submerged tube. The nitrogen pressure in the tube is equal to
the hydrostatic pressure created by the exiting bubble. Before each stage
measurement, the pressure transducer is calibrated by measuring the
hydrostatic pressure difference between two tubes installed a fixed vertical
distance apart in the liquid to be measured. These values are used to calculate
the multiplier value for the liquid level measurement. This self-calibration
minimizes the effects of temperature and long-term drift on the pressure
transducer, allowing a single pressure transducer to achieve a much higher
measurement accuracy (±.05%). The self-calibration theory is discussed in
detail by Dedrick and Clemmens (1984, 1986).

A single pressure transducer is used to measure three pressure lines (h1, h2, or
offset). The line to be measured is controlled by the three 2-way solenoid
valves on the manifold. The "bubble rate" is controlled by the two needle
valves on the manifold assembly labeled #1 and #2. The needle valve labeled
#1 controls the bubble rate for the pressure line used to measure h1. The
needle valve labeled #2 controls the bubble rate for pressure line #2 used to
measure h2. The needle valve is turned clockwise to decrease and counter­clockwise to increase the bubble rate. The suggested bubble rate is 1 to 3
bubbles/sec. The third solenoid valve is used to measure atmospheric pressure,
which will be used as the offset value.

The manifold assembly requires considerably more power compared to a
normal sensor. For this reason, an SP10 10-watt solar panel or AC power in
conjunction with a sealed rechargeable battery is recommended for the DB1
system.

References

Dedrick, A.R. and A.J. Clemmens, Double-bubblers coupled with pressure
transducers for water level sensing, Transactions of the ASAE, Vol. 27, No. 3,
pp. 779-783, 1984.

Dedrick, A.R. and A.J. Clemmens, Instrumentation for monitoring water
levels, Proc. of Agri- Mation Conference and Exposition, ASAE, March 3-5,
Chicago, IL, pp. 148-152, 1986.

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DB1 Liquid Level Measurement Sensor

2. Specifications

Measurement Range:
Option - 5 (0 to 5 psi/0 to 11.5 ft.)

Option - 15 (0 to 15 psi/0 to 34.5 ft.)
Option - 30 (0 to 30 psi/0 to 69 ft.)

Maximum Overpressure Range:
Option - 5 20 psi

Option - 10 45 psi
Option - 15 60 psi

Transducer Accuracy: ± 0.05 % Full Scale

Temperature Range: -25° to + 50°C

Supply Voltage: 12 Vdc

System Current Drain: 75 mA (Activated)

0.5 mA (Quiescent)

3. Installation

Valve Current Drain: 40 mA (Activated)
0 mA (Deactivated)

Maximum System Pressure: 100 psi

Mount the DB1 liquid level assembly to the enclosure back-plate using the
supplied plastic screw grommets and Phillips screws. Using the supplied
tubing cutter, cut sections of tubing for the nitrogen, h1, h2, and offset pressure
lines. Insert the h1 pressure line into the elbow fitting below the valve marked
#1. The line is installed correctly when it does not release without pressing the
red fitting into the valve assembly. Insert the h2 pressure line into th e elbow
fitting below the valve marked #2. Insert the offset line into the elb ow fitting
to the right of the valve marked #2. Insert the nitrogen supply line into the
elbow fitting on the right side of the manifold assembly.

Permanently install h1 and h2 a fixed vertical distance apart in the water (see
Figure 2, delta h). Maximize the fixed distance between h1 and h2, while
keeping h1 at least six inches below the surface of the lowest anticipated water
level. If the water level drops below h1 you will get irregular data readings.
The accuracy of the water level measurement is affected by the exactness of
the delta h measurement. To increase measurement accuracy, cut the end of
the submerged tubing at a 60 degree angle to decrease the gas bubble
deformation as it exits the tube.

2

The DB1 Liquid Level System requires a compressed gas supply. The most
common gas is a 225 ft
pressure relieved" pressure regulator. The pressure range set on the regulator
depends on the water level to be recorded. For example, if the DB1 system is
installed in a stilling well to measure stream level, and the stream level

3

nitrogen bottle with an appropriate "automatic