HIPOT AND ELECTRICAL SAFETY-TESTING FAQ
Frequently asked questions about hipot and electrical-safety testing
Q: How is ROD-L’s arc detection different from that of other manufacturers?
A: ROD-L hipot testers have the capability of detecting arcs as short as ten microseconds which may increase
the ability to catch faults that may become electrical hazards.
Q: Is hipot testing dangerous?
A: Yes due to the high voltage and high currents involved. However ROD-L units have safety features that nearly
eliminate operator hazard under normal testing conditions, including a two millisecond shutdown response upon
detection of failure, a ten microsecond arc-detection response, a ground-sense circuit that ensures the existance of
an escape path for the current if a catastrophic device-under-test failure occurs, and a rapid discharge of any
hazardous residual charge in the device-under-test at the end of each test cycle.
Q: Why doesn’t ROD-L offer hipot testers that supply both AC and DC voltage in the same box?
A: None of the regulatory agencies require that a product be tested with both AC and DC voltages. Instead they
generally offer a choice of testing a product with AC at a given voltage or with DC at a given voltage, which is 1.414
times higher than the AC value. The potential issue with using one hipot tester that offers both AC and DC in the same
box is operator error. The wrong voltage type (and therefore wrong voltage level) could be inadvertently selected by the
operator, and by the time the error is discovered products may have already shipped.
Q: How safe are ROD-L units compared to those of other manufacturers?
A: As far as we know, the combined multi-level safety features of ROD-L units make them the safest testers available.
Q: How often should the units be calibrated?
A: At least once a year, which is the minimum required by the regulatory agencies such as UL. However, units that are
in constant operation more than one shift per day, five days per week should be calibrated every six months. Note also
that ROD-L manufactures the ML11 and ML12 Test Load boxes for daily pre-shift functional checks of the hipot and
ground bond testers, as required by UL.
Q: Why can’t I just use an outside calibration house or perform my own annual calibration?
A: You can do that; however, with a ROD-L calibration you can also receive these advantages: 1) All necessary repairs
at no additional cost; 2) Experienced ROD-L technicians that can prevent units from malfunctioning and prevent
loss of production time; 3) Quick turnarounds, and even 24-hour turnarounds upon request for small additional fees;
4) Fully-guaranteed workmanship for a year, so with annual tester calibrations at ROD-L your testers would receive
continuous coverage for repairs.
Q: Is hipot testing destructive to my product?
A: Under normal conditions hipot testing will not damage the device-under-test. The reason is that the hipot tester will
always equalize the line and neutral voltage of the device-under-test before starting the hipot test, so the electronics
within the DUT would not be subjected to voltage. In other words, the high voltage will only occur between the conductive
chassis surfaces and the voltage-equalized internal electronics. However even if a wiring or insulation issue should
cause an unexpected fault, the ROD-L tester is also designed to shut down the test before serious damage may occur.
Q: Is the arc sensitivity level adjustable?
A: ROD-L determined more than 25 years ago, using internal company research as well as industry research, that arcs
as short as ten microseconds may lead to product safety failures. If a manufacturer were to use a hipot tester that had
an adjustable arc-sensitivity level, the following problems could immediately arise. First, the operator could inadvertently
select the wrong level, potentially invalidating this critical product safety measure and raising product liability claim
exposure for the manufacturer. And second, the manufacturer could use a less stringent arc-sensitivity level with the
unintended result of allowing inherently unsafe products to reach customers, once again exposing the manufacturer to
consequential product liability claims.
Q: How can I justify the cost of a ROD-L unit to do such simple tests?
A: Addiitonal safety protection for the test personnel in your company, liability protection from electrical faults that
could injure your customers, and reliability protection by preventing failures that could impact product performance in
the field. Money invested in good test equipment now may save you more down the road.
Q: How difficult is it to perform a hipot test?
A: Performing hipot tests is not very difficult. If the product being tested has a three-prong power cord, then just
plug it into the front of the hipot tester, connect the chassis ground sense wire from the front of the hipot tester to
the exposed metal surface of your product, wait a moment for the the green ready light to illuminate, and push the
start button. See the “Quick Start” guides for details. And for products that do not have a three-prong power cord,
you can use two alligator-clip wires - one for the HV out and one for the HV return - to connect them to the hipot tester.
Q: My product has a two-prong power cord. Can I still perform a hipot test?
A: Yes. There is a special set-up diagram in the back of all of our users manuals for connecting products with two-prong
Q: Can ROD-L hipot testers be interfaced with ROD-L ground bond testers?
A: Yes. The ground bond testers come with interface and jumper cables for interoperation with the hipot testers.
After connecting the testers, you can plug your product into one of the testers and push the start button to conduct
both tests in sequence as though they were one unit. Other types of ROD-L testers can interoperate the same way.
Q: What is the difference between the AVS5 models and the BVS5 models?
A: The BVS5 models can also monitor the real or resistive current in addition to the total current.
Q: What kind of warranty does ROD-L offer?
A: All ROD-L products are covered by a five-year warranty. However, in addition to this, if you send your units to us
at least once a year for complete calibration, we will repair any problem the unit may have at no additional cost. This
essentially provides a lifetime warranty on the units.
Q: Where should I set my trip currents?
A: There is no regulatory agency standard for this, primarily due to the great variety of designs and materials used
by manufacturers. So we recommend that an initial test sample of known good products be drawn (probably at
least 32 pieces for a good statistical sample). From the distribution of current readings at the required hipot test
voltage for that class of product, an upper limit can be determined-maybe at a 6 sigma or 8 sigma point, which
will become the trip current limit. This same method could be used for determining the real current trip point although
most manufacturers do not have a test requirement for this parameter. The real current is, however, an excellent
diagnostic tool. The undercurrent function is generally only used to verify that the power switch on the device-under-test
is in the “on” position. The same method could also be used to determine its setting, or an arbitrary setting of 1 or 2 on
the vernier dial could be used as more of a “go/no-go” type test. Otherwise we recommend that the undercurrent pot be
set to zero.
Q: What are the factory settings for the trip currents?
A: Unless otherwise requested by the customer, set the total current to the maximum (10 on the vernier dial which
equals 100% of the unit max), set the ‘real’ current to the maximum, and set the undercurrent to the minimum (0 on the
Q: What is the difference between the real current and the total current?
A: The real current is the portion of the total current that contributes to the dissipation of power and heat. It is also
known as the resistive current or the true leakage current, and it typically amounts to about 10% of the total current
for most products although for some types of products it may typically be much higher.
Q: What is the difference between the ML11 and the ML12 Test Load Boxes?
A: The ML11 presents a 0.06 uF capacitive load while the ML12 presents a 120 kOhm resistive load.
Q: I need a hipot tester which can set the voltage to various values. What model should I order?
A: Normally the variac knob on the rear panel of the M100/M500 units, or the potentiometer on the rear panel of the
M100DCs, allows the user to adjust the voltage from 0 up to the maximum voltage output level of his particular unit. For
users that need up to 6 discreet settings, we have an option which can be installed which provides 5 hard-wired settings
with the sixth remaining user-adjustable.
Q: ROD-L units appear to cost more. Why should I buy ROD-L units when I can buy cheaper ones?
A: ROD-L units offer a number of advantages over other manufacturers, including:
Safety - ROD-L units offer several operator-safety features that exceed the major electrical-safety agency
testing requirements, such as the two-millisecond shutdown time after detection of failures. ROD-L has also
received Consumer Product Safety Award recognition from the Professional Insurance Agents Association.
Quality - The accuracy, repeatability, and reliability that ROD-L units offer will help you perform more dependable
testing of your products before they leave your facility. This may mean higher product quality for you and better
sales in the long run.
Overall Cost Savings - Many ROD-L customers have used their ROD-L testers for decades without incurring
any costs or downtime due to repair service. And with our added safety features, you can look forward to a
lower risk of injury liability cost too.