Phoenix Contact / Signal conditioners and isolators

Two characters in the model number decide whether a device is rated for a hazardous area. And SIL 3 on these is conditional.

MINI Analog and MACX Analog are the Phoenix Contact signal conditioning ranges: isolating amplifiers, repeater power supplies, temperature transducers and converters. They sit between field instruments and the control system.

EX means intrinsically safe, and it is easy to miss

The most important thing on this page.

Two characters, and one device is certified for intrinsically safe circuits while the other is not. They do the same signal conditioning job otherwise.

If your plant has a hazardous area classification, fitting the non-EX version in an Ex i loop is a serious matter, not a specification detail. Read the existing device rather than matching on function.

The EX versions transmit supplied or active 0/4 to 20 mA signals from the Ex area to a load in the safe area. That direction is part of the design.

SIL 3 on these devices is conditional

Worth reading carefully if you are working to a SIL target.

Phoenix specifies the MACX MCR-EX-SL-RPSSI-I-UP as SIL 2 in 1oo1 and SIL 3 in 1oo2.

A single unit does not achieve SIL 3. The SIL 3 figure requires a redundant pair. If a specification calls for SIL 3 and someone has quoted one device, that is worth checking before it is installed.

The plain MACX MCR-SL-RPSSI-I is specified as SIL 2 to IEC 61508 with 3-way electrical isolation.

How the designation decodes

Take MACX MCR-EX-SL-RPSSI-I-UP-SP, order number 2924029.

Signal letters

The letters appear as input then output. So MINI MCR-SL-I-I is current in, current out, and MINI MCR-SL-U-U is voltage in, voltage out. A device with different letters is a converter rather than an isolator.

Function codes

MINI Analog signal conditioners

All are 3-way isolating amplifiers with screw connection, isolating input, output and supply from each other.

The configurable version and what it covers

The MINI MCR-SL-UI-UI is 6.2 mm wide and handles electrical isolation, conversion, amplification and filtering.

Standard signals include 0 to 20 mA, 4 to 20 mA, 0 to 10 V, 2 to 10 V and 0 to 5 V.

One configurable device covers most standard signal combinations, which means fewer part numbers on the shelf for a plant with mixed instrumentation. Worth considering when stocking spares rather than holding a fixed I-I and a fixed U-U.

A supersession

Phoenix lists the replacement part for 2864383 MINI MCR-SL-UI-UI as 2902036 MINI MCR-2-UI-UI-C.

If you are building new, specify the current part. If you are replacing one in an installed panel, the original may still be the right fit, and that is where we can help.

MACX Analog, the Ex and SIL range

Note the 5-way isolation on the two-channel unit. Two channels need isolation between the channels as well as input, output and supply. A 3-way device does not give you that.

HART passes through, if you set it up

These devices are HART-transparent, so a HART handheld or asset management system can talk to the field transmitter through the isolator rather than needing a connection at the device.

On a plant where transmitters are up a tower or in a pit, that matters.

The 250 ohm resistor

A useful detail on the 2924029: it has a 250 ohm resistor that can be switched in via DIP switches to increase HART impedance for low-resistance systems.

HART needs a minimum loop impedance to work. If HART communication is unreliable on a loop through one of these, that switch is the first thing to check before anyone starts replacing transmitters.

HART modem

What isolation actually buys you

Worth stating because it explains a common fault.

An isolating amplifier breaks the galvanic connection between the field device and the control system. That does three things: it stops earth loops between separately earthed equipment, it protects the input card from field-side faults, and it stops noise on a long cable run getting into the analog input.

If an analog reading drifts or is noisy and the transmitter checks out, an earth loop is a likely cause. An isolator in the loop fixes it, and is much cheaper than chasing it through the wiring.

See also the note about surge damage on instrument loops on our surge protection page. The two problems often appear together on the same long cable run.

The wider range

What we can supply

Current production. MINI Analog, MINI Analog Pro and MACX Analog across isolators, repeater power supplies, temperature and frequency transducers, plus HART modems. Quoted with a delivered lead time.

Superseded parts. Where the current replacement does not fit the existing panel or configuration, we can often find the original. Surplus and tested used.

Related

Phoenix Contact overview. Surge protection and Axioline I/O for the analog input cards these feed.

For process I/O from other brands see Omron CS1 process units and Siemens SM 331.

Send us your order numbers

Check whether the device you are replacing is an EX version, because that is two characters and it matters. If you are working to a SIL target, tell us and we will confirm the configuration the rating depends on. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Phoenix Contact GmbH & Co. KG. Phoenix Contact, MINI Analog and MACX Analog are trademarks of Phoenix Contact. HART is a trademark of the FieldComm Group. All trademarks, brand names and order numbers are the property of their respective owners and are used here for identification purposes only. Information on this page is for identification and does not constitute a hazardous area or functional safety assessment.