127. Wien 41 Mine Detector

a. General. The Wien 41 mine detector appeared in 1941. It was superseded in 1942 or 1943 by the Frankfurt 42 detector, the latter becoming standard German Army. In 1943 the Wien 41 was modified and, because of the development of the frequency-induction fuze, replaced the Frankfurt 42 detector as the standard mine detector.

b. Description. The Wien 41 mine detector (fig. 158) is an induction type. The search head is cast in two cylindrical, plastic sections. The shorter of the two sections is blue-gray in color and has a hinge bracket for hinging the extension handle to the search head. The longer section may be off blue-gray plastic or a mottled green and yellow plastic. The head of this section is rounded and contains a terminal opening for a fine adjusting screw. The short section screws into the longer section and is cemented in final assembly. The extension handle is of sectional construction and is made of aluminum tubing. The extension piece next to the search head is permanently attached to the search head at the hinge joint. To facilitate packing, this lowest extension piece will col-lapse against the search head. When the detector is dismantled, the extension pieces and search head are stored in a canvas case. The detector unit and the power supply are housed in a standard plastic pack case, the same type as that used with the Frank-furt 42 mine detector (par. 126). The off-on switch, voltage tester, and headset sockets are the same as in the Frankfurt 42 detector. The control box is different in that the knob will rotate continuously instead of in three positions as in the Frankfurt 42 detector. The search-head cable plugs into a socket on the right-hand end of the pack case. Two standard headsets are included in the detector set. The entrie detector set is stored in a wooden shipping case (par. 126) when not in use. The total weight of the detector set and shipping case is 58 pounds.

c. Functioning. The Wien 41 mine detector functions on the induction brigde principle. The inductance of the oscillator circuit is a horizontal coil in the search head. At right angles to this collar another coil is mounted in the search head and is connected to the amplifier. The output of the amplifier is fed to a rectifier and to a variable resistor. The rectified output from the ampilifier is fed to a trigger oscillator which gives an audible sig-nal in the headset. On approaching a metallic object, the balanced condition in the coils in the search head is upset, producing an audible change in signal.

d. Operation.

(1)

Assembling.

(a)

Open the shipping case, keeping it nearly vertical, and removing the pack case. Keep the pack case standing upright. The battery tends to lose its electrolyte if it is not kept upright.

(b)

Lay the shipping case down and remove the extension pieces and search head from their canvas case.

(c)

Thread the search-head cable through the extension pieces and assemble the extension handle.

(d)

Attach the pack harness to the pack case and sling it on your back making final adjustments for comfort.

Figure 158. Wien 41 mine detector.

(e)

Plug the headset in the socket marked Fernhörer.

(f)

Remove the control box from the control panel and hook it on your belt.

(g)

Remove the fiber tool from the control panel and replace the panel cover.

(h)

Lift the small metal flap on the right side of the pack case, and insert the plug of the search head cable into the exposed socket.

(2)

Operating.

(a)

Turn the off-on switch on the control panel to the on (EIN) position.

(b)

Hold the search head away from the ground and any metallic object.

(c)

Set the knob on the control box so the red dot shown.

(d)

With the fiber tool, turn the adjusting screw at the toe of the search head un-til a minimum or null signal is obtained.

(e)

Turn the knob on the control box clockwise until a maximum signal is obtained.

(f)

Readjust the adjusting screw on the search head until a minimum or null signal is obtained.

(g)

Continue step (e) and (f) above until it is no longer possible to obtain a mini-mum or null signal.

(h)

Turn the knob on the control box slightly counterclockwise and adjust the ad-justing screw until a minimum or null signal is obtained.

(i)

Continue step (h)above until it is no longer possible to obtain a minimum or null signal.

(j)

Advance the knob on the control box until a maximum signal is obtained.

(k)

The detector set is now adjusted for normal setting. If the knob on the control box is turned counterclockwise, a small-objects setting can be obtained. In this condition, the detector is more sensitive to small metal objects and less senitive to large metal objects.

e. Sensitivity. The Wien 41 detector is difficult to adjust for maximum sensitivity, and also difficult to keep in adjustment. When set for maximum sensitivity, there is a high-pitched not in the headset. With small-objects sensitivity, the detector will be silent until the object is very close.