EQUIPMENT AND SUPPLIES--Price AA Current Meter Magnetic Switch Closure Head: Modification To: "E - All WRD Employees" Subject: Price AA Meter...Modification Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Fri, 26 Jan 1996 11:09:54 -0600 From: "Dorothy E Greenwood, Secretary (Steno), Bay St. Louis, MS" Memorandum To: All WRD Employees From: Acting Chief, Hydrologic Instrumentation Facility Subject: EQUIPMENT AND SUPPLIES--Price AA Current Meter Magnetic Switch Closure Head: Modification This is to inform you that the Hydrologic Instrumentation Facility (HIF) and the Office of Surface Water (OSW) have modified the design of the Price AA Meter magnetic head contact chamber (mag head) so that it conforms to the standard rating for AA meters over the entire calibration range. The mag head was originally designed to replace the cats-whisker head for use in high conductivity, low-velocity conditions. One of the benefits of this design is that the mag head produces a much cleaner electrical signal when compaired to that of the cats whisker. With the introduction of modern electronic counters which require a clean electrical signal to function properly, use of the existing mag head meters increased. Many of these meters have been used to measure medium-to-high flow conditions which are beyond the capability of the existing mag head to measure accurately. Tests by OSW and HIF staff discovered that at velocities of 2.2 feet per second or greater, the mag head meter under-registers because the shaft rubs against the inside of the chamber. The HIF has implemented a modification to the contact chamber to resolve this problem. All mag head contact chambers which have been modified are identified by the letter "A" stamped on the top of the chamber. All users of mag head contact chambers should check for the "A" stamp on the top surface of the head before using it in velocities above 2 feet per second. Mag head contact chambers which use a circular magnet rather than a bar magnet already meet the standard rating over the full velocity range and do not need to be modified. The existing stock of magnetic head contact chambers in the HIF warehouse has been exhausted; however, a procurement action to replenish this item has been initiated. The modified contact chambers are available from the HIF under stock number 1101060 for $125.00. Should you wish to have an existing mag head modified for use in velocities above 2 feet per second, return it to the HIF, attention Aubrey Shaw. The cost for the modification is $50.00. If you have any questions concerning the modification or need ordering assistance, please contact the HIF at (800)382-0634. /s/ Frank S. Henry