Intrinsically Safe METRAHIT 27EX: A Milliohmmeter for Hazardous Environments

The Intrinsically Safe METRAHIT 27EX Milliohmmeter is a critical tool for ensuring safety and precision. Specifically designed for potentially explosive environments, including aircraft fuel tanks and outer skins, it’s vital for tasks like bonding tests and lightning protection assessments, where accurate measurements are paramount. Adhering precisely to operating instructions is essential for safe and efficient use.

With its compact and rugged design and safety certifications for explosive atmospheres, the METRAHIT 27EX is a dependable and versatile instrument for precise measurements in a wide range of industries, from factories to laboratories and on-site services. It’s a reliable choice for challenging conditions.

 

Features

• Measuring Ranges: Offers multiple ranges from 30 mΩ to 30 Ω for versatile applications.
• Resolution: High precision with 10 μΩ resolution for accurate low-value resistance measurements.
• Measuring Method: Utilizes a 4-wire Kelvin connection for precise results, eliminating unwanted influences.
• Data Storage: Can store up to 1200 measured values for record-keeping.
• Safety Certification: Designed for potentially explosive atmospheres with an “Ex II 2 G Ex ia IIA T4 Gb” designation.
• Certifications: Prototype test certificate (INERIS 05ATEX0040 ISSUE 04) and DAkkS calibration certificate included.
• Accessories: Kelvin probe, Kelvin clip, batteries, protective rubber holster, and hard case are part of the package.
• Warranty: Backed by a 3-year warranty for materials and workmanship, with 1 to 3 years of calibration coverage depending on the application.
• Indicator Displays:The LCD panel shows precise values with 4¾-place resolution and features two auxiliary displays, background illumination, and LED indicators for contact quality evaluation.
• Kelvin Connection: Suppresses unwanted resistance influences, ensuring highly accurate measurements.
• Offset Balancing: Enhances precision in lower measuring ranges with automatic offset balancing through thermovoltage compensation.
• DATA Hold: Quickly and reliably stores individual measured values, crucial for data integrity during measurements.
• Auto-Ranging: The milliohmmeter lets you choose the right measurement range automatically or manually.
• Power Management: It operates on two Ex approved batteries and auto-shuts down if idle for long or if voltage is insufficient, preserving battery life.
• Durable Design: The METRAHIT 27EX is compact and rugged, protected by a rubber holster with a tilt stand for use in tough conditions.

Features:

• Adjustment of Shunts in Instrumentation: The METRAHIT 27EX is suitable for precise adjustment and measurement of shunts used in instrumentation.
• Electrical Connection Testing: It can be used for testing electrical connections at conductor bars, including applications in open-pit mining, potential bonding systems, industrial settings, and household electrical systems.
• Cable Resistance and Wiring Testing: The milliohmmeter is effective for testing cable resistance, wiring integrity, and shunt resistors in printed circuit boards (PCBs) and thick-film circuits.
• Contact Resistance Measurement: It can accurately measure contact resistance in relays, contactors, power interrupters, and other electrical components.
• Fuse and Conductor Resistance Testing: The device is suitable for testing resistance in fuses and conductor resistance in power current circuits.
• Coil Resistance Testing: It can be used to test coil resistance in transformers, coils, small motors, and similar components.
• Aircraft Component Testing: The METRAHIT 27EX is versatile enough for testing discharge resistance on aircraft components, including outer skin components.
• Uninterruptible Power Supplies: It’s valuable for contact resistance testing in uninterruptible power supplies (UPS) to ensure their reliability.
• Welding Seam Contact Resistance: The instrument can measure contact resistance at welding seams to evaluate their quality and performance.

Specifications:

Technical Data
Indicator Displays
LCD panel (65 x 30 mm) with display of up to 2 measured values, unit of measure and various special functions.
Display / char. height	7-segment characters
	Main display: 12 mm
	Auxiliary displays: 7 mm
Number of places	4¾-place 30,999 steps
Overflow display	“0. L” appears
LCD Test	All display segments available during operation of the instrument are activated after it is switched on.
Background illumination can be switched on and off
OK LED (green)	lights up to indicate good contact at the measuring point
Error LED (red)	lights up to indicate interrupted test current (invalid measurement, poor contact when „0. L“ appears)
Power Supply
Batteries	4 x 1,5 V AA-Size: ARCAS Alkaline LR6 or Camelion Plus LR6
Service life	Measuring Function -Number of measurements *
	m at 100 mA > 500
	 at 10 mA > 80
	1 measuring cycle = 5 s
Additional consumption for:
Interface operation:	0.5 mA
LCD illumination:	40 mA at 6 V
Battery test	m range at 100 mA: Automatic display of the symbol when battery voltage falls below approx. 4.6 V. Instrument is shut down at less than 4.3 V.
Fuses
Fuse link
F1 for m/  ranges	500 mA / 600 V AC,
	switching capacity: 60 A at 600 V AC
F2 for batteries	250 mA / 125 V AC EX
Electrical Safety
Safety class	II per IEC/EN 61010-1:2010 /VDE 0411-1:2011
Measuring category	50 V CAT I
EX designation	CE 0080
	II 2 G Ex ia IIA T4 Gb
Tamb. = –10C ... +50 C	(Tamb. = ambient temperature)
Prototype test certificate	INERIS 05ATEX0040 ISSUE 04
Electromagnetic Compatibility (EMC)
Interference emission/ Interference immunity	EN 61326:2013 Tab A1
Data Interface
Data transmission (data transfer)	Bidirectional, optical via infrared light through the housing (read data and configure parameters)
With interface adapter as accessory
BD232	IR to RS 232C, serial, per DIN 19241, can be cascaded for multi-channel operation
USB-HIT	IR to USB 1.1 / USB 2.0, single-channel operation
Baud rate (MM  PC)	9600 baud
Ambient Conditions
Accuracy range	0 C ... +40 C
Operating temp. range	10 C ... +50 C
Storage temp. range	25 C ... +70 C (without batteries)
Relative humidity	45% ... 90%, no condensation allowed
Elevation	to 2000 m
Mechanical Design
Protection	IP 54
Dimensions	84 x 195 x 35 mm
Weight	Approx. 380 g with batteries (without GH18 protective rubber holster)

Certifications:

• CE Certificate
• EU Certificate

Resources:

• Data Sheet
• Operating Instruction
• Short Operating Instruction