User manual

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USB DrDAQ User's Guide 19

3.6.4

EL029 Reed Switch

A reed switch sensor can be used to detect the presence of a magnetic field such as

that from a bar magnet or an electromagnet. Alternatively, a simple, single-pole

switch can be connected to terminals inside the EL029.

Size

72 x 45 x 28 mm

Operating range

0 to 99%

Maximum response time

2 ms

The EL029 Reed Switch may be connected to either Ext 1, Ext 2 or Ext 3 on USB

DrDAQ.

To determine the optimum position for the magnet:

Hold the EL029 with its connecting socket towards you and the screw that fixes the lid

facing up.

The best position for the magnet is about half way along (towards the bottom) of the

right hand side of the EL029 case. The label on the bottom of the EL029 indicates this

position.

When a magnet is in place next to the EL029 the Reed Switch inside the EL029 closes.

This is shown in PicoScope and PicoLog by a change from 100% (switch open) to 0%

(switch closed). Note that this percentage is an indication of the proportion of the

sampling period that the switch is in the open state.

You may use the EL029 to connect a simple, single-pole switch (such as a micro-

switch) to USB DrDAQ. You will need to obtain a switch and some insulated connecting

wire. Remember to keep magnets or magnetic fields away from the EL029 when you

use it with an external switch. Magnetic fields will still make the internal reed switch

operate overriding the open setting of the external switch.

To connect the switch follow these steps:

1. Make sure that the leads from the external switch have about 5 mm of bare wire

to form the connections.

2. Remove the lid.

3. Put the EL029 on a firm flat surface, such as a table top, with the fixing screw

facing up and the connection socket towards you.

4. Unscrew the fixing screw.

5. Lift off the lid of the EL029 and put it and the screw to one side. The lid should

lift off easily.

6. Connect the wire.

7. Find the small terminal block, with two screws in its top, towards the back of the

EL029 circuit board.

8. Loosen the screws in the terminal block. Do not take them out altogether.

9. Thread the two wires from the external switch through one of the holes in the

bottom of the EL029.