Electrical Test & Measurement · Electrical Safety Testers
High-power safety tester with AC and DC withstand, insulation resistance, open and short detection and arc detection, in a four-channel and an eight-channel version with scanner expansion.
HG7804 (2 models) ·
A multi-channel safety test is decided less by the instrument than by the fixture it has to drive. The useful question is how many points can be reached without moving a lead, and what the tester does when one of those points is not connected.
Two models share one test engine and differ in how many channels they bring to the front panel: four on the smaller, eight on the larger. Both run an alternating withstand test, a direct withstand test, an insulation resistance test, an open and short check and arc detection, and both accept scanner hardware when the fixture outgrows the built-in channels.
The front panel carries the stop button at the left, a colour display showing the step, the function and the live reading, a keypad for entry, the channel terminals along the bottom edge and the high voltage output and return terminals at the right. The rear carries the mains inlet, the serial port, the fuse and the cooling vent.
The instrument raises its output over a programmed rise time, holds it for the test time and brings it down over a fall time, rather than switching the voltage on and off. All three are set per step, which is what allows a transformer or a wound component to be tested without the current spike that an instant step would produce.
During the hold it measures the current through the item and compares it with limits. A direct test adds a waiting period before the measurement, because the charging current of a capacitive item takes time to fall to the leakage level that is being judged, and the test ends with an automatic discharge rather than leaving the item charged.
Insulation resistance is derived from the current at a lower direct voltage, and the accuracy is quoted in bands because the current being measured becomes very small at the top of the resistance range. That is also why the material gives a separate, wider tolerance for the highest band.
Arc detection is a different measurement from the leakage comparison. It looks for a current pulse above a set amplitude and shorter than a defined width, which is what separates a flashover across a surface from a steady leakage path.
Count the points the fixture has to reach, then add the ones that will be added later. The difference between the two models is only the number of channels, so a fixture with more than four points makes the decision by itself; a fixture with fewer leaves the extra channels unused rather than harmful.
The second question is whether the points are tested in sequence or in groups. A stored sequence steps through the channels in order, and the group and comparison function, which the material lists as an option, is what allows results from several points to be judged together rather than one at a time.
The third is the connection check. Open and short detection runs before the high voltage, so a fixture with long leads or spring probes can report a bad contact as a connection fault instead of a failed insulation test. On a many-point fixture that distinction saves most of the time spent investigating failures.
The fourth is how the instrument is driven. A handler interface and a pass or fail output let it sit inside an automated cell; a serial port and a USB port let it be driven from software and store results, and the USB host port takes the stored groups with it.
The insulation resistance reading is only as good as the voltage actually applied across the item, and at the top of the resistance range the current is small enough that surface contamination on the fixture can dominate it. Cleaning and spacing are part of the measurement, not housekeeping.
Arc detection is adjustable, and its usefulness depends on the setting. Too sensitive and it trips on the fixture; too coarse and it misses the event it was installed to catch. The material gives the amplitude and pulse width it responds to, which is the starting point for setting it against a known good item.
The two models are distinguished by channel count only, so a specification written around one of them applies to the other except for that figure. Where a quotation compares them, the comparison is about the fixture rather than about the instrument.
Finally, the material does not state the input supply or the operating environment for these models. Those are ordinary requirements rather than optional ones, and they should be confirmed before the instrument is specified into a cabinet or a production cell.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| Output voltage | 0.05 to 5 kV, ±(1.0% of reading + 5 counts)Standard |
|---|---|
| Output frequency | 50 or 60 Hz, selectableStandard |
| Voltage regulation | ±(1.0% + 10 V) at rated powerStandard |
| Current range | 0.1 to 30 mAStandard |
| Current accuracy | ±(1.0% of reading + 5 counts)Standard |
| Rise time | 0.1 to 999 sStandard |
| Test time | 0.3 to 999 sStandard |
| Fall time | 0.1 to 999 sStandard |
| Output voltage | 0.05 to 6 kV, ±(1.0% of reading + 5 counts)Standard |
|---|---|
| Current range | 0.01 to 10 mAStandard |
| Current accuracy | ±(1.0% of reading + 5 counts)Standard |
| Voltage wait time | 0.1 to 99.9 s, direct mode onlyStandard |
| Discharge | Automatic at the end of the direct testStandard |
| Panel marking | MAX 5 kV rms and 7 kV DC at the output terminalStandard |
| Output voltage | 0.05 to 1 kV, ±(1.0% of reading + 2 V)Standard |
|---|---|
| Measurement range | 0.1 MΩ to 10 GΩ, with the current between 10 nA and 10 mAStandard |
| Accuracy at 500 to 1000 V, 1 MΩ to 1 GΩ | ±(5% of reading + 5 counts)Standard |
| Accuracy at 500 to 1000 V, 1 to 10 GΩ | ±(10% of reading + 5 counts)Standard |
| Accuracy at 500 to 1000 V, 10 to 50 GΩ | ±(15% of reading + 5 counts), printed although the range above stops at 10 GΩStandard |
| Accuracy at 50 to 500 V, 0.1 MΩ to 1 GΩ | ±(10% of reading + 5 counts)Standard |
| Discharge | Automatic at the end of the testStandard |
| Arc current range | 1 to 15 mAStandard |
|---|---|
| Arc range, AC | 1 to 15 mAStandard |
| Arc range, DC | 1 to 10 mAStandard |
| Minimum pulse width | 10 μsStandard |
| Open and short detection | Open and short detection is listed among the five test functionsStandard |
| Ground fault protection | StandardStandard |
|---|---|
| Ground continuity check | Standard, through the CONT CHECK socketStandard |
| Current RMS measurement | StandardStandard |
| Automatic gain control | StandardStandard |
| List scan display | StandardStandard |
| Safety interlock | Standard, through the INTERLOCK socketStandard |
| Memory | 100 internal groups and 500 on a USB drive, each with 100 stepsStandard |
| Comparator | Pass and fail LED indicationStandard |
| Interfaces | RS232C, USB host, USB CDC, USB TMC and handlerStandard |
| Scanner interface | OptionalOptional |
| Grouped test and comparison | OptionalOptional |
| Current offset | Current zeroing is provided; range and step not stated in the materialInformation required |
| Dimensions | 340 × 120 × 430 mm, given once for both modelsStandard |
|---|---|
| Weight | 5.0 kgStandard |
| Standard accessory | High voltage test lead, listed for both modelsStandard |
| Operating temperature and humidity | Not stated in the materialInformation required |
| Input supply | Not stated in the materialInformation required |
| Calibration certificate | Not stated in the materialInformation required |
| Ingress protection | Not stated in the materialInformation required |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| HG7804 | Four output channels | AC to 5 kV, DC to 6 kV, insulation to 10 GΩ | For a fixture with four test points |
| HG7808 | Eight output channels | AC to 5 kV, DC to 6 kV, insulation to 10 GΩ | For a fixture with eight test points, or for scanner expansion |
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
Four on the smaller model and eight on the larger one, using the channels built into the front panel. The channel count can be extended with scanner hardware, and the material gives an expansion ceiling of 120 channels in total. The practical limit is the fixture rather than the instrument, so count the points before choosing between the two models.
The output terminal is marked with a maximum that is above the direct voltage range given in the parameter table. The two figures are carried here as printed rather than reconciled, because the marking may refer to a different condition than the continuous test rating. The figure to design a test around is the one in the table until the supplier confirms otherwise.
It checks the connection before the high voltage is applied, so a probe that is not touching the item, or two probes that are touching each other, is reported as a connection fault rather than as a failed insulation test. On a multi-channel fixture that check saves the time spent investigating a false failure.
The number of test points, which fixes the channel count and any scanner expansion; the highest test voltage and current the product standard requires; whether the fixture has to be driven by a handler; and the supply and operating conditions on site, which the material does not state for these models.
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