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 detect increases in current flow that may lead to arcing in only ten millionths of second
(microseconds). This helps ROD-L testers shutdown abnormal tests faster than other testers and before serious
harm to the products or test operators can occur.
Q: Is hipot testing dangerous?
A: Yes due to the high voltage and high currents involved. However ROD-L units have safety features that virtually
eliminate operator hazard under normal testing conditions, such as 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 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: Because nearly all product manufacturers perform their hipot tests using the same AC or DC voltage type that
their tested devices use, ROD-L testers can only use that same voltage type in order to eliminate any potential
misconfigurations of the voltage-type that may be missed until after products have 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 will 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: Hipot testing with a ROD-L tester is not harmful to the device-under-test. One reason is that the hipot tester will
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 any voltage because the voltage would only occur between the conductive chassis
surfaces and the voltage-equalized internal electronics. And another is that even if a wiring or insulation issue should
cause an unexpected fault, the ROD-L tester is designed to shut down the test before any serious damage can 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, two potential problems could be introduced. 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 adopt an arc-sensitivity level that is too lenient,
potentially enabling unsafe products to reach customers and potentially increasing product liability claim exposure for
Q: How can I justify the cost of a ROD-L unit to do such simple tests?
A: By considering the additional safety protection for the test personnel in your company, liability protection from
electrical faults that may injure your customers, and reliability protection by preventing potential product failures.
And by considering that 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 difficult. If the products to be tested have three-prong power cords, then you can
plug them into the front of the hipot tester, connect the chassis ground sense wire from the front of the hipot tester
to the exposed metal surfaces of your products, wait a moment for the green ready light to illuminate, and push the
start button. See the “Quick Start” guide for details. And if the products lack three-prong power cords, then you can
use either an MP21 Hipot Test Probe or two alligator-clip wires - one for the HV out and one for the HV return - with
sufficient voltage insulation instead.
Q: My product has a two-prong power cord. Can I still perform a hipot test?
A: Yes. See the set-up diagram for connecting products with two-prong power cords in the back of your product
manual for details or contact us for assistance.
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. The real current
can serve as an even better diagnostic tool for detecting true insulation breakdown conditions than the total current.
Q: What kind of warranty does ROD-L offer?
A: All ROD-L products are covered by a five-year warranty. Furthermore, if you send your units to us at least once
a year for complete calibration then we will repair any problem the unit may have at no additional cost and extend
the warranty coverage for the subsequent year. This essentially provides a lifetime warranty on any such 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 suggest that after obtaining a sufficiently large test sample, you should consider setting
the total current trip level both high enough to prevent false failures and low enough to catch all potential insulation
breakdowns at the recommended hipot test voltage for your product. And if your ROD-L tester model can test the
real current as well as the total current, then we suggest that you use the same approach for setting the real
current trip point (even though most manufacturers do not have a test requirement for this parameter) since the real
current can serve as an even better diagnostic tool for detecting true insulation breakdown conditions than the total
current. Meanwhile, the undercurrent trip point setting is generally only used to verify that the power switch on the
device-under-test is on, so for the undercurrent trip point we recommend that you set it to a low setting in the range
of 1 to 2 on the vernier dial as “go/no-go” type test, or simply leave it at its factory default setting of 0.
Q: What are the factory settings for the trip currents?
A: Unless otherwise requested by the customer, the trip points on each tester are set to the maximum for the total
current trip point, the maximum for the real current trip point, and the minimum for the undercurrent trip point. On
the vernier dials on the back of each tester, the maximum setting corresponds to 10 (100%) and the minimum to 0.
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 six discreet settings, we have an option which can be installed which provides five hard-wired
settings with the sixth remaining user-adjustable.
Q: Why should I buy ROD-L units when I can buy cheaper ones?
A: ROD-L units offer several advantages, 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.