Fabrication of a Conductivity Sensor ENGR 121 living with the lab.

Fabrication of a Conductivity Sensor

ENGR 121

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The author of this information does not make any claims as to the validity or accuracy of the information or methods presented.

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Examples of Conductivity Sensors

www.globalw.comhttp://www.sensorex.com

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Raw MaterialsUltra High Molecular WeightPolyethylene

white = hydrogen

red = carbon

Chain molecules align more thanfor lower density polyethylene (packed together more tightly)

SOURCE: Phone order from

color: opaque white excellent electrical insulatortemp range: -22 to 180 F use indoorssoftening temp: 275 F machine with standard toolingtensile strength: poor hardness: shore D60-D69impact strength: goodlow friction

Also known as . . .poor-man’s teflon

Type 316 stainless steel rod or wireapproximately 1/16 inch diameter$0.46 per foot

Ultra high molecular weight polyethylene0.756 inch diameter bar$1.74 per foot

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Parts and Materials

UHMWPE rod - 3/4" diameter (cut to 1 3/4 inch long) - may be larger diameterspring-back type 316 stainless steel ( 0.064 inch diameter)22 gage solid wire (40 inches total)crimp-on snap-plug terminal, non-insulated male, 22-18 AWG, .156" plug dia (2 pieces)nylon barbed fitting - 3/16" tube ID, 1/8 NPT male (straight)brass hex nipple, 1/8 NPT male on both ends

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LatheYou must become familiar with theoperation and safety procedures of the tools before beginning the project.

tailstock

Q bit for center drilling workpiece

tailstock quick release

crank handle to feeddrill bit from tailstock

spindle and chuck

crank handle to move cross slidecrank handle tomove the carriagekey for chuck

carriage

cutting tool

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Safety Shield: Do not start machine if this shield is not in place.

emergency stop (hit this button to quickly stop machine)

Spindle Speed Control: This will be preset for you, so don’t adjust.

Lathe: Safety Features and OperationWith the safety shield closed and your safety glasses on, practice turning the machine on and off (turn off with both the off button and the emergency stop). Practice moving the carriage, cross-slide and drill bit in the tailstock.

red off button

green on button

forward (for drilling and facing) and reverse (for beveling)

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Milling Machine: Loading Workpiece into ChuckMake sure the workpiece is securely clamped in the vise before beginning work.

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Download “2_cond_a_loading_workpiece.wmv” video. Store video in the same directory as this presentation. Click on the picture to play video. 8

Lathe – Watch Out for Rotating Parts

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Download “2_cond_b_rotating_parts.wmv” video. Store video in the same directory as this presentation. Click on the picture to play video. 9

chuck

workpiece

tool

Safety Checklist:1. Avoid contact of tool with chuck

2. Keep hands, hair, clothing, and jewelry away from rotating parts

3. You should feel it when the drill bits drills through the far end of the workpiece (only advance tool slightly past this point)

4. Are your safety glasses on?

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Safety Rules for Freshman Labs1. Do not operate any machine unless you have

• completed a hold harmless form• been trained to operate the machine• been authorized to do so by the instructor or lab monitor

2. When using rotating equipment such as milling machines, drills and lathes, • securely tie long hair back to remove the possibility of it falling below your face• do not wear loose clothing• remove lanyards or jewelry hanging from your neck or wrist

3. When using power tools like milling machines, drills and lathes,• clamp the workpiece in a vise or chuck before drilling or cutting• never hold or restrain the workpiece with your hand• make sure all safety guards are closed before powering up machine• never leave a running tool unattended

4. When working in the lab, • always wear approved eye protection• take common sense precautions & avoid “horse play”• keep work area clean & organized• never use your own power tools• only use lab facilities to complete activities required for ENGR 120, 121 and 122• report damaged equipment, unsafe activities and accidents to the instructor

Do not begin to fabricate your pump until you have carefully read the operating and safety instructions above and agree to operate the equipment in a responsible manner. You must sign the safety contract before beginning fabrication.

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Positioning for Facingliving with the lab

Download “2_cond_c_positioning_for_facing.wmv” video. Store video in the same directory as this presentation. Click on the picture to play video. 12

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Facing and Beveling

Download “2_cond_d_facing_and_beveling.wmv” video. Store video in the same directory as this presentation. Click on the picture to play video. 13

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Center Drilling

Download “2_cond_e_center_drilling.wmv” video. Store video in the same directory as this presentation. Click on the picture to play video. 14

Create Threads in Each End using 1/8 NPT Tap

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Mark Locations for Conductivity Probes

center mark

½ inch

location for inserting probes

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Drill Holes for the Probes

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1) Rest the ends of the workpiece on the parallels (different parallels may be used)2) Use a #53 drill bit (0.059 inch diameter) so the 0.0625 inch SS rod will be press fit into the hole3) Drill 0.625 inches deep (this is 1/8 of an inch shy of going all the way through)

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Cut 1/16 inch Stainless Steel Rod (already done for you)

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Press the Rods into the HolesThis is a little tricky. Go slow and keep the rod in place with one hand while slowly tightening with the other.

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Press Terminals onto SS Rods using Vise (or tap on with hammer)

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Crimp Terminals onto Stainless Rods

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Crimp 20-inch Piece of 22-Gauge Wire onto TerminalBe sure to strip the ends of the wire before crimping

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CONGRATULATIONS – You’re Done!!!!