German installed meters are of no better design than late type hi-shock USN meters of comparable size and scale face.  For the most part they exist in the same varieties and types found in USN submarines.  The majority, being ammeters & voltmeters, operate on the D'arsonval principle.  
          As nearly as can be determined portable meters for various purposes are not supplied in the types and quantities found aboard USN submarines.  
          Certain meters and instruments have been made available to BuShips Code 660 for detailed exploitation.  
          All German submarines are provided with electronic ampere hour meters by means of which the condition of the main battery is determined.  
          External shock mounting in form of bonded rubber mounts in compression, tension, and shear are used extensively on components which have meters and instruments installed in then and on the meter or instrument housings where mounted separately.  
July, 1946
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  1.  Introduction  
          The scope of this report is to present in a general manner the observations obtained in calibrating and repairing German meters at the shipyard.  
          In addition the German application of meters and instruments may be obtained from the various German instruction books referenced thruout the other reports on type 9C vessels.  
          The following listed meters and instruments have been forwarded to BuShips Code 660 for detailed exploitation and reference should be made to their reports when they become available.  
                  (a)  Electrolytic Ampere Hour Meter  
                  (b)  Voltmeter  
                  (c)  Combination Ammeter and Voltmeter  
                  (d)  Megger (0-12 Megohms)  
                  (e)  Megger (0-20 Megohms)  
  2.  Descriptive  
          German meter elements vary in size dependent upon use.  They are found in housings designed for surface, semiflush, or flush mounting as required by the given installation.  These housings are from 1-1/2" to 3" in diameter and except for the smaller ones up to about 3" in diameter are made from pressed steel stampings.  A removable front cover is provided for protecting the meter elements from foreign matter.  Suitable shatterproof glass is assembled in the cover to protect the meter element from foreign matter and provide a means of viewing the scale face.  "Antiglare" feature normally found in USN installed shipboard meters was not observed.  Meters installed as part of a switchboard or distribution board have studs protruding from the rear of the housing.  Meters which are mounted directly to the hull and not assembled with other equipments have their studs brought out at the bottom into a connection box which is an integral part of the meter housing.  A watertight seal for the connection box is obtained by means of socket type rubber gaskets.  Ammeter shunts are mounted in this box.  Terminal boards of this type described under General in Report 2G-9C-s65 are used in these applications.  
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          Most meter housings of the smaller size are molded phenolic for surface or flush mounting with provisions for making connections at the rear.  Tapped metal inserts are provided for the external and internal connections.  
          Dial faces are graduated in an arc of 90° in most cases and never more than 270°.  Provision is made for zero centering without removal of the front cover.  
          Since the large majority of installed meters are D.C. type it is presumed that the maximum design effort was spent on these.  While the results of details exploitation and any laboratory tests as may be made on meters sent to BuShips Code 660 are not available as yet, the following observations are set forth:  
                  a)  Meter elements are not designed nor manufactured to approach laboratory instrument requirements to the degree that USN meters do.  It is believed German meter elements are adequate for the purpose intended.  
                  b)  All operate on the D'Arsonval principle.  
                  c)  Permanent magnets of "Alnico" characteristics are used.  However, in the larger elements, the Germans did not use this feature to advantage in space saving.  
                  d)  Workmanship and manufacturing methods are equal to but not better than USN meters.  
                  e)  Accessibility for maintenance and calibration is not as good as normally found in USN meters.  
                  f)  Ammeters are designed to be used with either a 60, 75, 200, or a 300 M.V. drop shunt.  Calibrated leads are not provided by the manufacturer.  This required lead size is found on the scale plate directly under M.V. drop marking.  Calibration is accomplished at the installation.  
                  g)  Two position adjustments are available for balancing rather than the three normally found in USN meters of this type.  
                  h)  Base plates are in general considerably larger than those in USN meters.  
                  i)  It is not believed that German meters would meet USN meter high shock requirements.  
                  j)  Voltmeters D.C. ohms per volt vary from 100 to 200 ohms.  
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          The German favored tubular shunt which consisted of a suitable number of approximately 1/4" O.D. tubes assembled between the end blocks.  An advantage of this type of shunt is that it minimizes the need for additional support when mounted in other than the vertical position.  Cooling fins are not provided nor are they as necessary with this type shunt.  
          In the smaller sizes where only one bar is required the German resorted to the flat bar shunt similar to those normally found in USN installations with the exception that the flat bar usually had several deep waves incorporated in it to improve ventilation and decrease space required.  
          The following types of meters are found installed in German circuits, electrical and electronic:  
D.C. millimeters
with usual multitude of scale ranges.
D.C. millivoltmeters
with usual multitude of scale ranges.
D.C. ammeters
with usual multitude of scale ranges.
D.C. voltmeters
with usual multitude of scale ranges.
A.C. voltmeters
with usual multitude of scale ranges.
A.C. milliammeters
with usual multitude of scale ranges.
A.C. millivoltmeters
with usual multitude of scale ranges.
A.C. ammeters.    
A.C. voltmeters.    
Frequency meters - usually electrical type; however, in several cases vibrating reed type is used.
Electrolytic Ampere Hour meter - designs vary to provide for energizing from a 200 M.V. drop or a 300 M.V. drop shunt.
Temperature meters - D.C. millivolt meters energized from thermocouples.
Salinity Indicator - D.C. voltmeter
Main Engine Torsional Vibration Indicator Meter - Scale graduated in degrees - is actually an A.C. voltmeter
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          While no standard allowance list appears to be available it is believed the following list of portable meters enumerates the majority of those placed aboard.  No separate meter room or locker is provided, the instruments being placed in care of the interested department for care and stowage, much the same as in USN practice.  
Oscillograph (3" scope)
D.C. Ammeter and Voltmeter in common box.  Shunts for various ratings are assembled on a separate board.
Voltmeters - Various scale ranges
Tube and Fuel Oil Fire and Flash Point Test Meter - D.C. voltmeter scale suitably graduated.
  3.  Conclusions  
          German design and application of meters and instruments are satisfactory for purposes intended.  There is nothing unique in design or manufacturing methods as nearly as can be determined from observations made of the installations on board or in the instrument room.  Reference should be made to BuShips Code 660 reports on meters shipped there for study.  
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