Download this handout is a presentation on the use of the 188a that is used by

“188A/C9970 Voltage test set,
accessories and Testing procedures”
Figure 1, 188A Voltage Detector (for the purpose of this presentation C9970 will not be repeated although totally relevant).
188A has two main purposes:
A) Protects the user while conducting tests for “Potentially” dangerous
voltages (up to 20,000 Volts AC and 6,000 Volts DC).
**If initial test is testing objects that could exceed 20,000 Volts AC initial
test is performed with tested rubber gloves.** Then if all tests safe, rubber
gloves are removed and objects retested bare handed.
B) Indicates the presence of “potentially” hazardous voltages (The 188A
doesn’t indicate what the potential is just that there may be one).
The 188A is a capacitive coupled device (two conductive surfaces separated
by an insulator) that separates the hand of the user from the internal
circuit.
When do you visually inspect and test the 188A.
A)
B)
C)
D)
When received with a 193A test plug
Self test before use and after use to insure proper operation
Monthly with 193A test plug
Annually with 1188A Test set
Inspecting the 188A:
- Visually inspect for any defects
- Visually verify test date (Expires 1 year after test with 1188A)(Tag on
trigger is means of identification of last test date).
- With trigger depressed green LED illuminates then with finger on
check contact and other finger onside of carbide tip red flashing LED
illuminates (Fingers may need to be wet as dry skin does affect
sensitivity).
Perform “Tip to Tail inspection” Monthly:
A) Remove conductive cap and inspect carbide tip (carbide to insure
penetration through paint or rusted surfaces) Verify tip secure.
B) Progress down shaft looking for cracks or scratches (these would
render item unsafe for use).
C) When reaching red and green “LED”, Press trigger and observe
Green LED illuminates…then touch “test contact” (on side) and
carbide tip (never press finger to the sharp end always touch side to
avoid injury)..Red LED illuminates and Green goes out. The Red LED
will stay lit till trigger is released (this is a designed feature to enable
out of sight readings) (Light emitting Diodes “LED” won’t burn out or
break if unit is dropped as there is no filament just 2 electrodes
surrounded in a conductive material that passes current and
illuminates) this test verifies battery and internal circuitry working.
D) Then progress to “DC” ground post and verify secure. Also touch
ground post and check contact with trigger depressed to verify
E)
F)
G)
H)
I)
internal circuitry operation…Green LED will go out and Red LED
illuminates.
Progressing down shaft you will see where unit can be separated to
change battery…on the newer units there is a set of arrows that are
aligned when tightened to help avoid over tightening…on the older
units align the thumb stop with the LED’s.
Now continue down the shaft to the “Flash Guard Rings”. The flash
guard rings need to be crack free, intact and clean from any debris
(Flash Guard Rings are designed to compact the size of the 188A.
Electrical current travels on the outside of an object and for it to
travel any distance through air the voltage level has to be extreme or
a current path needs to be present like debris or even smoke creates
a current path, Thus by designing the flash guard rings the 188A is
electrically 2’ long) .
Progressing to the thumb stop…**If this is missing the unit is not to
be used**. Thumb stop allows for the user to apply pressure on the
tip of the unit when testing but not allowing the hand of the user to
slip into the flash guard area thus shortening the distance of the tip
to the user increasing potential hazard to the user and negating the
safety of the 188A.
Progressing to the magnetically connected trigger (normally
black…on some of the older designed AT&T units this is blue). There
is no physical connection between the trigger and internal circuitry
of the 188A. This is done by having a magnet that is under the trigger
that slides under the trigger, down the shaft as the trigger is
depressed and places it over an internal set of contacts that are
metallic and pulled together magnetically and completes the internal
circuitry for operation……Green LED illuminates when this done.
Notice on the side of the trigger should be a date of “last test” date
recorded. This is placed when tested with the 1188 test set and is
valid for 1 year. When the unit is new the date is only good for 9
months out of the box. There have been several changes to this label
over the years. First was a aluminum tag the was placed and when
written on would dent from the pen so the date couldn’t be rubbed
off, then came colored tags that were non conductive that had the
same yearly color code as the copper color code for cable pairs so
that you could determine if unit was safe or due test.
0
Blue
1
Orange
2
Green
3
Brown
4
Slate
Color coded Labels
Yearend dates
5
6
7
8
9
** If the ink was rubbed off you could still tell the year of last test.
Then lastly due to availability of colored tags just a bland color tag
was used and if date not present unit needs retest. Also tag’s should
be placed on left side of unit if right hand user and left side if left
handed user for ease in insuring visually that unit has been tested in
the last year.
J) Progressing down handle is a vague set of instructions that describes
use of the 188A…although they aren’t complete they serve as a good
reminder of how to use the unit.
K) Lastly is the snap hook mounted to the base of the unit. This
provides two purposes :
1. Ensures the internal unit and the handle are made to be used
together. Unscrew the handle and insure this is correct (Gold clip
& Gold tube….Silver clip & Silver tube).
2. Used to ensure unit doesn’t fall when being carried aloft (verify
spring in clip works and hook not deformed).
L) With unit separated inspect that screw rings are clean and crack free,
“O” ring gasket in place and tube is perfect cylinder shape and
securely attached.
M) Progressing to the bottom of the tube pull battery out of base,
ensure connectors are attached securely to top of battery (in the old
AT&T style units an “Eveready 522A” battery was recommended as
the tube was slightly smaller and most 9V batteries wouldn’t fit). The
Eveready batteries aren’t required with the new unit’s just need to
ensure that the battery fits without distorting the shape of the tube
or if it does a different manufacture of battery needs to be used.
N) Also look inside tube while the battery is removed and observe that
cellophane wrapper that separates the metal of the battery to the
metal of the tube is in place (If this is missing the 188A will not
operate correctly). Also while looking into the tube insure the foam
bump stop at base of internal circuit board is in place to protect the
board for any damage from battery.
O) Reassemble the 188A don’t over tighten and always do self test to
insure 188A is operating correctly after being disassembled.
ACCESSORIES to the 188A
A) Conductive cap: Cap is made with conductive material impregnated
into plastic. Cap provides several functions:
- Protects user from sharp carbide tip when not in use
- Protects carbide tip when not in use
- used to perform induction test with use of W1BU cord
To test conductivity of cap press carbide tip firmly into cap surface
and while trigger pressed place finger on check contact and opposite
end of cap….red led indicates continuity (note: real dry hands often
make continuity test difficult as this is a very low current used for
verifying continuity thus fingers may need to be moistened).
B) “B” Temporary bond: This is used after identifying that objects in
work are de-energized. Place tested rubber gloves and with “B”
temporary bond connected to known ground, objects stay deenergize and safe in our work area. If item becomes energized “B”
Temporary bond is designed to emit smoke and may wiggle. If “B”
Temporary bond does start to smoke or wiggle due to becoming
energized place rubber gloves and leave work area immediately till
power issue is resolved.
- 5’ foot in length
- Can use up to two cords together and if extra length is needed #6
copper wire of any length may be used.
- Muller clips (Two Sizes for a reason)
** Small clip #24A (25amp) used for attachment to known ground
source (#6 vertical, strand or ground bus bar).
** Large clip used for attachment to object to be grounded…Larger
to be able to attach to multiple size objects…Internal copper strip in
larger clip #11A (100amp) is to insure continuity to both sides of clip
to cord.
- Test with 188A for continuity (end to end) or brown meter before
and after use to verify operation.
- Visually inspect attachment from cords to clips tight and no
damage entire length of cord.
- If you arrive on a scene and find a “B” Temporary bond in place,
Contact your supervisor and ask if any issues have ever been noted
at this location before. Then perform all tests as if the bond was not
in place and when tests completed to and safe work area is
determined put on rubber gloves place your “B”Temporary bond
over the other and then remove the foreign bond. Destroy the
foreign bond as you have no clue as to what may have happened to
the cord and how long it has been in the field.
C) W1BU Cord: This is used when performing induction test when
188A shows red LED and further testing required.
- 20 to 25’ in length when pulled straight, Compact due to spring
cord.
- Test before and after use with 188A or Brown meter for continuity
to insure operation.
- can use up to 4 cords together if necessary.
D) 193A Test Plug: Used monthly to verify electrical sensitivity.
- 120 volts AC reduced to 60 volts ac through the use of two
resistors (150k ohms each) connected in series making a voltage
divided circuit that limits current to a level below the threshold of
feeling thus making the tip save to touch with bare hand and safe to
leave plugged in.
** 188a should always be tested on 193A after every battery
change, monthly and any time unit is dropped**
E) 1188A Test set – used annually to verify correct operation of the
188A or used anytime unit is suspected of not working correctly.
- High voltage test:
Checks the dielectric strength of the 188A’s housing and subjects
30000 Volts AC to the DC ground post for 10 seconds energizing the
metal tube exposing any leaks over 50 volts or 15 micro amps from
the housing of the unit.
- Circuit test
50 Volts on tip produces red light flashing, 20 volts on tip and no
lights flashing.
- Fail is indicated with a light and buzzer
USING THE 188A IN THE FIELD:
Testing for AC (50 to 20000 Volts)
A) Always perform self test before using.
- Self test: visually inspect looking for cracks or defects
- Test operation of green LED (by pressing trigger) and internal
circuitry by touching check contact (with trigger still depressed) and
tip to get Red LED
- Verify test date
B) - Approach object with trigger depressed (always insure object is always
tested before any contact is made with any part of your body).
C) 188A is designed to store readings “locking” in case you can’t see LED’s
while touching object in question (as long as trigger remains depressed).
D) If object tests red release trigger and repress to retest….often if static
charge 188A will sense voltage and indicate hot but will also allow enough
current to dissipate so on second attempt item will show safe and is safe.
E) If after second attempt RED LED still illuminates then induction test must be
preformed: This often happens when working from a bucket as the rubber
tired vehicle doesn’t provide continuity to ground.
1. Get metal object of at least 6” long that will be inserted into earth
ground
2. Get Tested Rubber gloves
3. Test conductive cap and insert onto back end of 188A
4. Inspect W1BU cord and test for continuity.
5. Visually inspect ground area where metal object is to be inserted
(customer power riser on pole…secondary and primary)(customer
owned equipment of any kind)
6. Place rubber gloves and insert metal object (screwdriver of at least 6”
works well for this)
7. Now remove rubber gloves and test object that was inserted into
ground with 188A to insure not inserted into any live item that was
under the surface of the ground that couldn’t be visually observed.
8. Now connect one end of W1BU cord to known ground and other end to
ball on end of conductive cap.
9. Approach object with two fingers on conductive cap and two fingers on
handle of 188A with a firm grip with trigger depressed (here again is
where really dry hands or really lose grip will affect the ability of the
188A to dissipate any static reading and give you a true reading).
10.If you have done the induction test released and repressed the trigger
and object still test “HOT” then safely back away and secure the area.
**Securing the area means insuring that no one else from our
company or others goes into that work area without knowing a hazard
is present**
This means coning off area or placing ribbon until hazard is removed
and staying on site till further investigation takes place.
Voltmeter Test:
The reason for this test is often good enough continuity from the
conductive cap to the handle of the 188A isn’t obtained, Dry skin, dirty
cap, or other so this test eliminates all doubt.
For the this test you will need a voltmeter, tested rubber blanket,
one tested “B” temporary bond, tested W1BU cord and a second
technician or supervisor.
A) Place tested rubber blanket within 5’ of metal object that has been
placed into ground.
B) Lay Voltmeter on blanket and set reading to AC.
C) Connect one end of tested “B” temporary bond to screw driver and
the other to one lead of the voltmeter, now connect tested W1BU
cord to the other lead of voltmeter and other clip to the carbide tip
of the 188A.
D) Now approach the object (the main purpose of the 188A in this test
is to keep you safe it has no real bearing to this test) and touch with
the tip of the 188A to the object. The second person observes the
voltmeter (not holding it as it is resting on the rubber blanket) a
reading below 50 volts is a safe reading to proceed with
work(induction identified) a reading of over 50 volts and the work is
not safe and power company needs to be notified to assist…we do
not leave an unsafe condition.
E) When the power company arrives we share our findings and assist
with helping identifying the hazard. It is very important that we use
the same ground reference point as them if they find no hazard to
insure we have the same results.
**To correct issues with induction generally additional verticals
added to the line helps drain off the induction.
**Common power issues generally stem from insulators failing and
current traveling to ground.
Testing for AC Voltages above 20000 Volts
A) Use Tested Rubber gloves for initial test.
B) After all objects test safe with rubber gloves retest bare handed
Testing for DC Voltage (6-2000 Volts)
Areas you will find DC voltages are any place where assembly line
production or where speed control of equipment has to be precise as DC
is easier to regulate than AC, also Central office is an example of a
location with DC Voltages ( other examples: machine shops, Rail
systems, Elevator systems, old factories, trolley systems, power rooms
and hospitals).
For this test you will need tested Rubber gloves, 188A, two tested
“B” Temporary bonds and a coil of #6 copper wire.
A) Test for AC superimposed over DC
(Telephone ringing voltage (AC) over DC is a good example of this)
-
Test everything with tested rubber gloves on…verify safe (AC over
20000 Volts).
- Test everything bare handed….verify safe (AC under 20000 Volts).
(Before and during AC test and DC test Do Not allow any part of your
body to come in contact with any object till verified safe)
B) While testing for AC, identify Ground bus Bar.
(Example: in C/O Labeled “Ground” copper bar)
C) With tested rubber gloves on,
- Connect “B” temporary bond large clip to known ground
- Connect “B” temporary bond small clip to DC Ground post
(Can use up to two cords and as much #6 copper as needed to test
everything in area)
D) With Rubber gloves remaining on touch all objects with carbide tip
then press trigger verify reading release trigger and remove from
item being tested. DC draws an arc easily thus the change in testing
procedure.
E) Do not remove rubber gloves till all objects have been tested safe
and cord removed from Bus bar.
Notes assembled by David Carbee from: “BSP” 081-705-102
(12/ 2009)