16 



2. Solder one end of 18 gauge wire to the other prong on the 6 V 

 relay, and solder the other end to the negative end of the 

 electrolytic capacitor (Ci). 



Wiring the Sensor Relay to the Unijunction Assembly, 

 Sensor-indicator Assembly, and Battery 



Materials 



(2) length of two-conductor speaker wire (see below for length) 



(1) 12 V lantern battery 



(6) 'quick-disconnect' wire connectors 



Instructions (refer to Fig. 14) 



1. The following leads should be extending from the PVC 'T' 



a. Two leads of two-conductor speaker wire (attached to the 

 sensor relay). There may be a third lead if a spore trap is 

 going to be attached to the sensor relay. 



b. Two leads of 16 gauge stranded single-conductor wire 

 (attached to the LED and switch of the sensor indicator 

 assembly). 



2. Wire the sensor-indicator LED and switch to the sensor relay 



a. Select one of the speaker wire leads and strip about 15 mm 

 of insulation from the end of each strand. 



b. Solder the copper (positive) strand to the 16 gauge lead 

 attached to the switch (e). 



c. Solder the silver (negative) strand to the 16 gauge lead 

 attached to the LED (f). 



3. Cut two lengths of speaker wire long enough to extend 

 through the PVC tubing supporting the sensor unit, along or 

 under the ground, and into the instrument shelter once the 

 apparatus has been installed in the field. Within the shelter, 

 one wire will connect to the 12 V lantern battery and the 

 other wire will connect to the unijunction assembly. 



4. Solder 'quick-disconnect' plugs to the ends of the copper and 

 silver strands of each speaker wire lead extending from the 

 PVC 'T' and also to the ends of each strand of the speaker 

 wire that will attach to them. These plugs will allow the 

 sensor unit to be removed and attached, if necessary, with- 

 out disturbing the remainder of the apparatus. 



5. Wire the sensor relay to the unijunction assembly. 



a. Connect one of the long lengths of speaker wire to the 

 speaker wire selected for 2, above. 



b. Insert the other end of this wire through the drilled hole in 

 the hygrothermograph base and plexiglass stage, 



c. Solder the positive (copper) strand to the junction of the 



