hi,welcome to my first instructables ,im tonny

yesterday i was repairing a microwave oven and i need to check the HV input which is connected to the magnetron,but of course its impossible to measure -3~4 kv dc without a HV probes,and probes from company like fluke,tektronix are expensive ,so i make my own ,and i decided to share this on instructables ,hope you like it

hv probe is a probe designed to measure HV lines,it have a ratio (1000:1 in mthis one) so if the input to the HV probes is 1000v / 1Kv it will puts out 1V dc/ac depends on the input

heres the spec of the one i made today


operating voltage: 0.1-15KV , 0.1-12.5KV cont , up to 15kv for 5 sec

internal resistance: 10MOhm + 10KOhm

lets make it

Step 1: Connecting All the Resistors

- get 10 pieces of 1MOhm 2 watt resistor , and a piece of 10KOhm 2 watt resistor (pic 1,2)

-cut all the resistor leads ,left 5mm of the leads for sodering (pic 3) -solder all the resistor in series,and put the 10k resistor on one end of the resistors (important,if you place it wrong the probe won't work) (pic 4)

Step 2: Insulate the Resistor

to prevent arc we need to insulate the resistor

insulate it by wrapping the resistors with 4 layer of heat shrink tubing we can expect at least 2.4kv insulation from those,because each tubing was rated for 600v

begin by wrapping all the 1MOhm resistor,leave the 10k resistor (pic 3)

the heat shrink tubing size: 2 layer of 5mm tubes and 2 layer of 6mm tubes

Step 3: Wiring the Resistor and Wrap the Whole Thing

after wrapping the 10MOhm resistor (10X1M) we can connect all the necessary cables

Step 4: Make the Resistor Housing

after wrapping and wiring the resistor time to completely isolate it

cut a piece of 3/8 inch garden hose and some fiberglass rods

length of the hose: depends on resistor length ,see pic 1 ,make sure it cover the whole resistor array

then before putting the resistor into the hose reinforce the hose with fiberglass rod and super glue,this also make the hose to stay straigt so it wont bend the resistor leads and help protecting it then wrap it with rubber/pvc tape ,

then we can put the resistor into the hose and seal both ends with tissue and superglue ,see pic 5~11

the resistor is done

Step 5: Make the Pointy End Probes (i Dont Know What to Call It)

starting with 10mm2 full copper cable,strip the insulator to get copper bare wire (pic 1,2 ,or you can also use a nickel plated copper nails to make something similar

use an angle grinder to sharpen one end of it

get a pvc pipe end cap and drill a hole in the middle ,try to make a hole that is the same size as the copper,so the copper doesnt move easily,or try using a superglue to hold it in place

then get a 2 part epoxy like jbweld or other epoxy glue and make it looks like the one in pic 6

theres where it gets tricky to get a good result you have to carefully shape it ,heres the trick,while the glue wet ofc it will stick to your hand if you touch it with bare hand,touch it with wet hand use two fingers to make it the epoxy wont stick to a wet hand,keep molding it for at least 15 minutes until the epoxy can hold its shape then you can leave it to cure for few hours

Step 6: Finish the Outer Housing

after finishing the previous step we can finally put them all together begin by connecting the HV cable from the resistors to the copper and insert a whole thing into a 3/4inch PVC pipe , i prefer not to glue both end caps so if i accidentally burned the resistor i can replace it

Step 7: Testing This Is the Final Step and the Moment of Truth,if You Did Every Step Properly It Will Work Just Fine

thats it for my first instructables,thanks for reading,see ya,have a nice day

Step 8: VIDEO

<p>Another way to isolate all resistances:</p><p>- Take a PVC tube of 16mm diameter</p><p>- Glue one end a PVC cap, drilled to pass the test probe</p><p>- Install the resistor chain carefully in the axis of the PVC tube</p><p>- Flow the PVC tube in molten paraffin to embed the assembly.</p>
<p>Good idea. This is probably a lot safer than just using the probes on a multimeter.</p>
It's also good for extending the voltage range of meters that can only read 1kv, like the cheap RadioShack meters.

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