The OSS-PC1 Pygmy Current Meter is a world recognised design instrument for measuring the velocity of water in shallow natural water couses and canals, small pipes, laboratories and river models. The OSS-PC1 complements the OSS-B1 universal current meter to provide solutions for all velocity measuring applications.
Operation
The OSS PC1 Pygmy Current meter consists of a streamlined body which housed the sensing mechanism, an encapsulated reed switch, and the propelleer shaft which has a permanent magnet mounted such that each rotation of the shaft produces a pulse from the reed switch. The pulses are conducted through a lead to the surface where they are counted by a current meter counter. The velocity of the stream is proportional to the rotationals of the propeller.
The following equation is used to calculate the velocity.
V = K x N + C
Where:
V is the Velocity
K is the Hydraulic pitch of the propeller
N is the Number of pulses counted
C is a constant determined by rating tests
Each OSS PC1 is calibrated in accordance with AS 3778.6.3 - 1992/ISO 3455-1976. Each OSS-PC1 is provided with a calibration certificate and rating tables.
Features
The OSS PC1 superior design offers:
Streamlined nickel silver body.
Low start velocity a magnet impulse device with no mechanical retardation of propeller generates signals.
Ease of replacement of the Reed Switch Assembly
Encapsulated Reed Switch to resist damage from dropping or knocking.
A.B.S. and moulded foam carry case
'Hockey Stick' style Sewer Rod to position meter in pipes from a man hole.
Suspension Methods
Option 1 The OSS PC1 is supplied with 3 x 0.5 m sections of 9mm diameter Stainless Steel Rod for locating in the water stream. These rods are graduated every centimetre and numbered each decimetre. A detachable base is used to position the rod on the stream bed or channel floor. A Top Setting Rod is available to allow the OSS PC1 to be relocated along the rod without having to withdraw the rod from the stream. This allows the user to continuously observe velocities at different depths of the stream.
Option 2 The OSS PC1 can be supplied with a clamping adaptor (Part No. PYG13A) to allow it to be attached to a 20mm diameter rod. This configuration is better suited for higher velocity measurements.
Propellers
Propellers are fitted with a unique retainer to prevent accidental loss during Sewer gauging. The OSS Pc1 is supplied with two propellers, ie, a 50mm diam. X 0.25m pitch and a 50mm diam. X 0.05m pitch. They are made of anodised aluminium alloy. Other propellers are available.
Current Meter Counters
The OSS PC1 provides a pulse to a Current Meter Counter. HYDROLOGICAL SERVICES offers three counters to suit all applications. All models record up to 40 pulses per second.
CMC - 2: is a simple pulse counter which requires a stop watch to accurately measure the stream velocity.
CMC - 20: is a more complete counter which can be set to count pulses for a specific time period (10-200 secs). The counter stops when the time period has elapsed and shows a digital reading of the number of pulses.
CMC - 200: is the top of the range counter with the option of setting the time period or the number of pulses to be counted.
Meter pulses are converted to velocities by reference to the rating table for the specific propeller used.
Specifications
The OSS PC1 is supplied in a basic kit as follows: Propeller Type 1 and 3, 2.5m Connecting Lead, Tools, Oil, Spare Bearings, 3 x 0.5m length, 9mm diameter Rods, Detachable Base, Calibration Tables and Carry Case.
Propeller Specifications
Propellers are fitted with a unique retainer to prevent accidental loss during sewer gauging.
Type 1
Size - 50mm x 0.05m
Maximum Velocity (m/s) - 2.0
Start Velocity (m/s) - 0.035
Range of Component Effects - +/- 30 degrees
TYPE 3
Size - 50mm x 0.25m
Maximum Velocity (m/s) - 6.0
Start Velocity (m/s) - 0.035
Range of Component Effects - +/- 10 degrees
TYPE 5
Size - 30mm X 0.05m
Maximum Velocity (m/s) - 2.0
Start Velocity (m/s) - .050
Range of Component Effects - +/- 20 degrees
