The AMPTEC 720A Digital Micro-Ohmmeter with AutoRange -

USAF NSN 6625-01-555-1150RH 

Ideal Keithley 580 Micro-Ohmmeter Replacement as selected by the USAF 

The AMPTEC 720A Micro-Ohmmeter has the identical ranges, resolution and it offers slightly better accuracy than the obsolete Keithley 580 Ohmmeter. The AMPTEC 720A is an accurate, affordable,  seven range, four wire Kelvin based Digital Micro-Ohmmeter and is available with Auto-Range capability.  Resistance measurements can be made from 10 µOhms to 200 KOhms on seven ranges with 4 ½ digit (20,000 count or 50 ppm) resolution on the AMPTEC 720A.  With 0.03% basic accuracy for all the ranges, except the low 200 milliohm range (0.05 %) the 720A micro-ohmmeter has accuracy that includes U.S. N.I.S.T. traceable calibration certification. The AMPTEC 720A Ohmmeter is used to test electrical resistance on a wide variety of applications such as motors, transformers, contacts, copper coils, components, bonds and a host of metal to wire connection integrity (i.e. splices) tests.  The unit's high contrast high intensity LED display (25,000 lumens) is also readable in direct sunlight environments. 

Four Terminal Configuration, Low thermal EMF binding posts and more.

Four Terminal Kelvin configuration (Voltage high, Current high, Voltage low and Current low) automatically eliminates major sources of resistance measurement errors such as test lead length resistance and test lead connection contact resistance. The ohmmeters gold plated low thermal emf 5 Way binding posts also make it easy to securely connect bare test wires, spade lug wiring and DMM style banana jacks. The AMPTEC 720A Ohmmeter's 5-way gold plated copper tellurium input jacks are low thermal emf which helps provide accurate low level resistance measurements when temperature differences and dissimilar metals (thermocouple effect) would normally be a measurment problem.   

Resistance Measurements made Easy and Accurate - AMPTEC 720A Micro-Ohmmeter

The AMPTEC 720A digital Micro-Ohmmeter makes 4 terminal Kelvin resistance measurements on a variety of devices including the following: Winding resistance and shorted turns of: small motors, alternators, transformers, generators, coils, solenoids, relays, wire spools, chokes and ballasts.  Measuring inductors like transformers, motor wings, coils and chokes couln't be easier using the AMPTEC 720A Ohmmeter.  The AMPTEC 720A's current source has a compliance voltage of > 1.5VDC.  A higher compliance voltage allows the ohmmeter to rapidly charge any inductance associated with making the resistance measurement.  The higher the ohmmeter's compliance voltage (drives the constant current source) the more stable and quicker an inductors (i.e copper coil) resistance can be measured. All AMPTEC 720 series test lead and probe sets are a minimum 48" length, dual banana termination at the ohmmeter end (call the Sales Department at AMPTEC RESEARCH for any custom requirement).   

The AMPTEC 720A Digital Micro-Ohmmeter can easily measure the contact resistance of: switches, resistive trimmers, mating connectors, relay contacts, circuit breakers.
Bonding or Connection resistance measurement: any metal to metal connection, crimp lug connections for cables, weld joints, PCB to switch or connector integrity testing, bolted joint resistance of cable connections and earth ground testing.
Component testing, matching and sorting: Resistors (all types -metal film, wirewounds), pots, strain gauges, shunts, IC substrates, thick film circuits, small motors and small transformers, chokes, thermistors, fuses, extruded copper wire, Ni-Chrome wire, all alloys of wire, heating elements, printed circuit board clad resistance, plated through holes, plating thicknesses.

An optional rechargeble battery powered version of the AMPTEC 720A Micro-Ohmmeter is available - Ideal for field portable and "On-the-Go" resistance measurement applications. Internal single or dual battery pack(s) provide hours of mobile field use of the AMPTEC 720A Micro-ohmmeter.

Option "110" Test Lead Pouch - fitted to the top of the AMPTEC 720A Ohmmeter its zippered storage area has room for Kelvin probes, Kelvin Clip leads and the operator manual.

Option “232” RS232 Remote control plus local Auto-Range - For automating resistance measurements of  “components or parts” (sorting, recording, results printing and more...),  the AMPTEC 720A Digital Micro-ohmmeter offers an optional RS232C serial interface. The option "232" actually provides two capabilities in one. First, the option "232 provides full remote range and resistance measurement control. The readings can be automatically taken over via the serial interface to a controller (PC).

Secondly the RS232 option includes "Autorange" -The Option "232" (isolated RS232) microprocessor I/O also provides the AMPTEC 720A Micro-Ohmmeter with local or manual Autorange capability (deselect all push-button ranges for Auto-Range mode). In Auto-Range mode, the AMPTEC 720A Micro-Ohmmeter automatically determines the optimal range for the resistance measurement under test. The unit's digital display indicates both the measured value, for example 123.45 and also the magnitude (milliohms, ohms, or Kohms) automatically in Auto-Range mode. 

All AMPTEC 720 series test lead and probe sets are a minimum 48" length, dual banana termination at the ohmmeter end (call the Sales Department at AMPTEC RESEARCH for any custom requirement).  

Option "300" Gold Plated Four Terminal Kelvin Clip Test Lead Set The Kelvin Clips open to a ½" for connection to wires, lugs, etc. (shown with standalone option KCS clips which accept banana jacks) - note all four jaws of the clip must make a metal/metal connection to measure correctly.
Option "350" Large Four Terminal Kelvin Clip Lead Set - The large Kelvin Clip ends (PVC composition handles) with attached cables, open to a 1 ¼" for connection to larger lugs, bus bars and bolt heads.

            Close-up photo of Option"402" Kelvin Micro-Probes

Option "402" 4 Terminal Kelvin Microprobes - similar to Option 403, (see photo above ) except each probe has two fine steel tips (spring loaded) with 0.05" separation (red and black handheld probes - 1 ea).

Option "403" 4 Terminal Kelvin Mini-probes - (photo shown above)  Each probe has two spring loaded, gold plated,  steel tips with 0.18" separation. (one red and one black handheld probe). Excellent general purpose Mini-Probe, and along with the Option "300" Kelvin Clip Leads is included with the 720A Pouch Test Lead Package. 
Option "519" Rack Mount Adapter includes support tray, flush panel with cutout & hardware that accommodates a standard NEMA 19" Instrument rack cabinet enclosure. 

For a data sheet of all the ohmmeter accessories, test leads, probes and options that are compatible with the AMPTEC 720A Digital Micro-Ohmmeter and related AMPTEC Failsafe Ohmmeters select here.