Robert Vollrner Cose Institute of Technology Cleveland, Ohio
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Beam Protective Device for an Automatic Analytical Balance
The knife edge of an analytical balance can be damaged if the user forgets to arrest the beam before changing the beam loading. Damage of this sort can be greatly lessened by a device which emits an audible signal if the balance door is raised with the beam in an unarrested position. We have been successfully using a warning device of this k i d on the automatic balances in both our general chemistry and analytical chemistry laboratories. Such a device can be installed on a balance in about 2 hrs. at a parts cost of about four dollars. Figures 1 and 2 show the general installation and wiring diagram for installing the audio-device on an Oertling balance, Model H05. The procedure is as follows: Remove thc left side panel, held by six self-tapping screws, for drilling and mounting of the parts. Mount the buzzer on the inside and the buzzer microswitch on the outside of the panel. The switch is positioned so that when the sliding door is closed its left protruding edge compresses the microswitch bar opening the circuit. Wire the buzzer and switch in series. Then run the two wires along the top and down the back of the panel. An interlock switch or a 2 f t length of cord will facilitate the removal of the case for easy servicing. Run one of the wires over to the light bulb. Pinch the wire under the light bulb flange; or if preferred, solder the wire to the copper strip which connects to the bulb ring contact. Run the other wire to the balance microswitch. Connect to one of the wired terminals on the switch. If the buzzer operates with the beam arrested, remove the wire and connect to the other wired terminal on balance microswitch. By means of a pair of diagonal pliers, twist the panel slightly, a t point 1 on Figure 1, in order to eliminate any side play of the panel and to guarantee proper actuation of the buzzer microswitch.
FIX WZFR IMIDE'C~E. BUZZES WHEN EALNUICL 19 IWlTCilLD ON AND FRONI
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MICRO SWITCHW l R E i o MlCRO WiKH
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Figure 1.
Figure 2.
Volume 40, Number 2, February 1963
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