The PD686 Loop Powered Meter has been discontinued. The following products should be considered for replacement: PD685, PD6606 & PDA2801. Customer should read specifications carefully or call tech support to determine if replacement product is suitable for application.


  • NEMA 4X, IP67 Loop-Powered Field-Mount Process Meter
  • 4-20 mA Input
  • 1.0" (25.4 mm) 3½ Digits LCD Display; -1999 to 1999
  • 1 V Drop
  • HART® Protocol Transparent
  • Operates from -40 to 85°C (-40 to 185°F)
  • Operates from -40 to 40°C (-40 to 104°F) for Canadian Installations
  • Zero & Span Potentiometer Adjustments for Easy Field Scaling
  • Plastic NEMA 4X, IP67 Enclosure
  • FM Approved & CSA Certified as Intrinsically Safe & Nonincendive
  • Conformal Coated PCBs for Dust and Humidity Protection
  • One ½" Conduit Hole (Rear, Top, Bottom or None)
  • Pipe & Panel Mounting Kits
  • Stainless Steel Tag Available

Why Use Loop-Powered Meters?

The most basic decision a user wishing to display a 4-20 mA signal on a digital display has to make is: should the meter be powered by line voltage or should it be powered by the 4-20 mA loop?

There are three main benefits of using loop-powered devices:

  • No additional power required
  • Easy wiring
  • Additional digital displays can easily be added in the same loop

The following diagram illustrates how a loop-powered meter is wired. Notice there are only two connections made to the meter.

Loop-Powered Connections

For more information on loop-powered meters, check out Fundamentals of Loop-Powered Devices and Loop-Powered vs Line-Powered Meters white papers.


The PD686 is an FM Approved, CSA Certified intrinsically safe and nonincendive, NEMA 4X, IP67 loop-powered indicator that is easy to install and program. It can be seen from considerable distance and even in bright sunlight. The fact that this meter is loop-powered means that there is no need to run additional, costly power lines into a hazardous area. The meter gets all of the power it needs from the 4-20 mA loop and its 1 V drop results in a minimal burden on the loop. The meter features a wide -40 to +85°C operating temperature range and is available with a ½" conduit hole in a location of your choice for easy installation. Calibration is a quick two-step process involving the adjustment of only high and low, non-interacting potentiometers.

Except where noted all specifications apply to operation at +25°C.

Input4-20 mA @ 30 VDC maximum
Display1.0" (25.4 mm) LCD, 3½ digits; -1999 to +1999
Accuracy±0.1% FS ±1 count
ApprovalsFM Approved & CSA Certified as intrinsically safe with entity, for use in Class I, II and III, Division 1, Groups A, B, C, D, E, F, & G; T4; hazardous locations.
Nonincendive for use in Class I, Division 2, Groups A, B, C and D.
Suitable for use in Class II and III, Division 2, Groups F and G
FM certificate number: 3016598.
CSA certificate number: 1111348
Additional FM ApprovalsIntrinsically Safe, Class I, Zone 0, AEx ia IIC T4
Entity ParametersUi = 30 V, li = 175 mA, Ci = 0 μF, Li = 0 μH, Pi = 1.3 W
See Control Drawing LIM686-2 (Dwg No 1155) for complete installation instructions.
Decimal PointUser selectable
CalibrationTwo-step; non-interacting zero and span
Calibration Range4 mA input: -1000 to +1000;
20 mA input: between 20 and 2000 counts > 4 mA display
Display Update Rate2.5/second
Maximum Input Current30 mA
Maximum Voltage Drop1 V @ 20 mA
Operating Temperature-40 to 85°C
Canadian installations: -40 to 40°C.
Storage Temperature-40 to 85°C
Relative Humidity0 to 90% non-condensing.
Printed circuit boards are conformally coated.
EnclosureImpact-resistant glass filled polycarbonate body, color: gray; impact-resistant clear polycarbonate cover; NEMA 4X, IP67
ConnectionsRemovable screw terminals accept 12 to 26 AWG
Conduit HoleOne ½" conduit hole provided, see Ordering Info.
Overall Dimensions5.51" x 3.15" x 2.56" (W x H x D)
(140 mm x 80 mm x 65 mm)
Weight12 oz (340 g)
Warranty2 years parts and labor. See Warranty Information and Terms & Conditions on for complete details.


Calibrator Connected to Input Signal PCB

Calibrator Connected to Input Signal PCB
Control Loop Connected to Input Signal PCB

Control Loop Connected to Input Signal PCB
Control Loop Connections with Backlight (2-Wire)

Calibrator Connected to Display PCB

The display PCB may be removed from the enclosure for bench calibration. Loop Jumper must be installed on Input Signal PCB to maintain loop.


Units: Inches (mm)

PD686 Dimensions

Dimensions and Wall Mounting Information

Pipe Mounting Kit

The PDA6845-SS is a stainless steel pipe mounting kit with two mounting holes. It provides all of the necessary hardware to mount the PD686 to a 2" pipe.

PDA6845-SS Pipe Mounting Kit

PDA6845-SS Pipe Mouting Kit

Panel Mounting Kit

The PDA6844 is a panel mounting kit for the PD686. It provides all of the necessary hardware to mount the PD686 meter to an equipment panel. This panel mounting kit is not intended to provide waterproof protection to the panel.

PDA6844 Panel Mounting Kit

PDA6844 Panel Mouting Kit


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