redirecting to Microhmmeters in 4s.
The ATO-400 micro-ohmmeter is specifically designed for sub-station applications to measure EHV circuit-breaker contact resistances, bushing contact joints, or any low resistance. This microprocessor-controlled micro-ohmmeter can accurately measure low resistances ranging from 1 micro-ohm to 300 milli-ohms at any test current from 10A to 400A. Resistance readings are displayed directly in micro-ohms or milliohms. No calculation is required to compensate for lead resistances. A custom switching power supply helps keep the ATO-400's weight low at 40 lbs (18.1 kg) and makes it an ideal unit for field use.
The ATO-400 outputs an un-filtered direct current from 10A to 400A to the resistance load being measured. A rugged, 16-key alpha-numeric keypad is used to control the unit. The burn-in time for a typical resistance test can be selected from 5 seconds to 60 seconds. An Auto Test Mode is also available and can be initiated simply by applying the sensor cables' leads across the two points of interest. This feature is very convenient when measuring a sequence of several resistance values in a breaker contact.
The ATO-400 features a back-lit LCD screen (20 characters by 4 lines) that is viewable in both bright sunlight and low-light levels. The unit can store up to 63 records (each may contain up to 64 readings) in Flash EEPROM. Test reports can be recalled for review, or they can be transferred to a PC via the built-in RS-232C or USB interface ports. A Windows® XP/Vista-based software application is also provided with each unit and can be used to transfer test records to a PC. Test records can also be reviewed, printed or exported in text or Microsoft® Excel format via the software application. The ATO-400 is furnished with two #1/0 15-foot test cables. Custom test cable lengths are available as an option. Heavy-duty, welding-type, C-clamps are also available as an optional accessory. These can be used to connect the test cable leads to a wide variety of bushing sizes, bus-bars and other conductors requiring low-resistance test contacts. The ATO-400's power supply is thermally protected and the contact-sensing inputs are protected against static-discharge damage.