C.5 Other Equipment and Assemblies
This section lists and describes other equipment and portable discharge measuring devices that may be included in the hydrometric operational inventory. Some of these items may form part of the kits supplied by most current meter manufacturers.
A conventional wading rod is an option supplied with all Price current meters. It usually consists of four ~13-mm diameter graduated rods that assemble to make up a rod 2.44-m long. The length of these rods can be extended by ordering additional sections for use in large culverts or low bridges. An adjustable sliding support attached to the rod holds the meter and meter tailpiece in place. Electrical connections are provided for hook-up to headsets or counters. To adjust of the depth of observation setting, the rod must be raised from the streambed.
European and Australian manufacturers provide three-piece 9-mm-diameter graduated rods with the small current meters. The top section of the rod is drilled to accept the negative plug from the counter. If a shorter length of rod is required, e.g. for placing the meter in a small-diameter culvert, an alligator clip, modified to accept the cable plug, may be used with either of the lower sections.
For the larger model meters such as the OSS B1, and the OTT C31 and C5, a 20-mm diameter conventional rod is provided. The current meter can be clamped directly on this diameter of rod while adapters may be supplied to accept Price AA and small current meters such as the OSS PC1 or the OTT C2. The rod is supplied in 1-m sections, which are graduated in centimetres and numbered decimetres. A suitable length of connector cable(s) to match the meters is needed. A meter relocating device for this rod is described later in this section.
Top setting rods (Figure C-27) are designed to securely position Price AA or Pygmy current meter at any desired depth while the technician wades the stream. Adapters for small propeller meters are available from the manufacturer. The design incorporates a graduated stainless steel hexagonal rod and a parallel round aluminum rod (earlier versions are round and square respectively), connected by a cast aluminum handle. The current meter and tailfins are attached to a sliding support on the base of the aluminum rod which is allowed to slide vertically for rapid positioning of the meter. A vernier on the handle permits automatic setting of the meter to any desired depth (Table C-10).
After the wading rod is placed into a stream and the water depth is read from the graduated hexagonal (round) rod, the vernier is used to position the current meter to the desired depth. Most models have an electrical connector mounted on the handle to attach the headset or revolution counter.
Figure C-27. Top setting wading rod.
Table C-10. Vernier settings for top setting rod.
Vernier setting |
Actual current meter position |
Exact water depth |
0.4 up from streambed |
Twice water depth |
0.2 up from streambed |
Half water depth |
0.8 up from streambed |
