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Hydrological Equipment

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Type A Chart Recorder, A-71 English

Item No.:
45.00 LBS

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The US Type A-71 Water Level Recorder provides continuous, unattended recording - with high accuracy regardless of range. The Type A-71 has been improved and perfected over the years and today it is still the world-wide standard in quality and reliability for river hydrography and other installations where long term operation is required.

A Type A-71 Recorder uses a strip chart and pen marker to provide a permanent on-site record of water level fluctuations. Both metric and English models are available. The recorder is precision-made to respond to 3 mm water level change at 1:5 scale (or 0.01 ft. at 1:6 scale) using a 254 mm/10 inch float. The float is used with either a beaded float line or a float tape (graduated in meters, decimeters, centimeters or feet, tenths, hundredths). A clock drive controls the movement of the strip chart at a constant speed. The pen marker moves laterally across the chart and reverses direction at each margin to provide an unlimited recording range.

The recorder stands on a three-legged cast metal base, and has an ABS plastic cover with a full face gasket and a clear viewing port. Safety features to prevent accidental record loss include an automatic friction roller engaging knob and a safety pawl attachment.

Strip charts are printed on high quality paper to minimize humidity effects. Several days of record are normally visible with recorder in operation. The 25 cm wide A-25 chart is for metric measurement and the 10 inch wide A-10 chart, for English measurement. A disposable cartridge pen is provided as standard equipment.

Time scales are designated by the number of inches of chart utilized in one day. The chart speed specified most frequently is 2.4 inches (6.1 cm) per day at which speed the chart will last about a year. Standard time scales are easily interchanged in the field. With the QMT drive this is done by switch selection - with other drives by substituting gears.

Two chart drives are available. Timer and time scale gears can be easily changed in the field.

Quartz Multispeed Timer (QMT) - The most frequently specified, the QMT uses a 6 volt battery. It can be used with solar cell battery charger for 5 year minimum operation. Time scale gears need never be changed again since seven switch-selectable scales are available.

Negator Spring Drive with Chelsea Clock - for time scales up to 12.2 cm/4.8 inches per day. This chart drive uses a large spring which slowly unwinds from one drum onto another, driving the instrument's chart for 4 1/2 months or on special order for 6 months. The Chelsea clock regulates the rate at which the spring unwinds and thus the speed of the chart.

Gage Scales:

The ratio between the chart record and water-level changes is known as Gage Scale, e.g. a 1:5 Gage Scale means that the record will be 1/5 actual size (Standard English Scales are multiples of the ratio 1:12). Instruments may be converted in field from English to metric system, and vice versa.

Also required for operation and sold separately are one of each of the following:

Float Pulley

Beaded line or float tape



End Hooks