FM Approvals Canadian Standards Association

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.


  • 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

Conduit Installation Instructions

  1. Remove the printed circuit board from the enclosure.
  2. Connect appropriate size conduit fittings to the hole provided. For enclosures without a pre-drilled hole, the installer must make a hole in accordance with the instructions for the particular conduit fitting being installed.
  3. Connect conduit (with attached hubs) to the enclosure. Conduit hubs must be connected to the conduit prior to being connected to the enclosure. Use only conduit hubs that are designed to maintain NEMA 4X or IP67 ratings.
Note: Please read FM Approved & CSA Certified Loop-Powered Meter Intrinsic Safety Barrier Connections (LIM686-2, Dwg No 1155) – for more information pertaining to the conduit holes.

Mounting Instructions

  1. Remove the enclosure cover from the base.
  2. Insert mounting hardware into mounting holes in enclosure base.
  3. Secure the enclosure base to the mounting surface using the inserted hardware.
  4. Re-attach the enclosure cover to the base.


The only tools needed for calibration are a calibrated current source and a small slotted / flathead screwdriver.

Calibration Connections

To access the input terminals it is necessary to remove the enclosure cover and the Display PCB. This is done by loosening the four screws on the enclosure cover and removing the cover. Completely loosen the left screw that holds the Display PCB to the enclosure and loosen the right screw about four turns so the Display PCB remains attached to the enclosure. Rotate the Display PCB 90° to gain access to the Input Signal PCB. Next, connect a calibrated current source.

Decimal Point Selection

The decimal point jumper array is located in the lower right corner of the Display PCB next to the display. It is labeled DP1, DP2, DP3. Place a jumper over both pins of DP1 for a display of 199.9, DP2 for 19.99, or DP3 for 1.999.


LO and HI calibration controls are located to the left of the display. Apply a signal equal to 4 mA and adjust the LO control to display the desired reading. Apply a signal between 16 and 20 mA and adjust the HI control to display the desired reading. Complete the calibration procedure by making any minor adjustments to the LO and HI controls.


Installation of the meter involves removing the Display PCB from its enclosure and connecting a ½" conduit fitting to the hole provided. Refer to PD686 FM Approved & CSA Certified Loop-Powered Meter Intrinsic Safety Barrier Connections diagrams (LIM686-2, Dwg No 1155) for further details. Wall mounting holes are located in each corner of the enclosure.

Loop Connections

Disconnect power to the loop and install the meter as illustrated in Figure 2 and the PD686 FM Approved & CSA Certified LoopPowered Meter Intrinsic Safety Barrier Connections diagrams (LIM686-2, Dwg No 1155) supplied with the instrument. Replace the enclosure cover.

Removing Display PCB From the Loop

The Display PCB and Input Signal PCB are connected together with one black and one red wire. The wires are soldered to the Display PCB and connected to a screw terminal connector on the Input Signal PCB.

To remove Display PCB:

  1. Loosen the four screws on the enclosure cover and remove the cover from the enclosure base.
  2. Completely loosen the left-side screw holding the Display PCB to the enclosure and loosen the right-side screw four turns so the Display PCB remains secure to the enclosure.
  3. Rotate the Display PCB 90° to gain access to the Input Signal PCB.
  4. Install Loop Jumper over both pins to bypass Display PCB and allow the signal to flow through the Loop Jumper. The display turns off when jumper is installed.
  5. Disconnect the black and red signal wires from the screw terminal connector.
  6. Loosen completely the right-side screw and lift Display PCB from enclosure. Care should be taken to prevent static electricity from damaging the electronic circuitry.
  7. Restore enclosure cover to the base to prevent contamination of components.

Restoring Display PCB to the Loop

  1. Remove enclosure cover as described above in step 1.
  2. Secure Display PCB to enclosure using right-side screw; do not tighten screw to allow rotation of Display PCB while accessing Input Signal PCB.
  3. Connect red wire to S+ terminal and black wire to S- terminal.
  4. Remove Loop Jumper to allow the signal to flow through Display PCB (save push-on jumper by placing over one pin only).
  5. Tighten screws holding Display PCB and install enclosure cover.

Servicing Display PCB Outside the Loop

Two modes of input signal allow the user to remove the Display PCB for service without interrupting the loop as indicated above and operate the Display PCB at another location in a nonhazardous area. The loop remains connected to the Input Signal PCB while the Display PCB is absent for service. The user may operate the Display PCB at another location by connecting a signal to "S+" and "S-" wires on the Display PCB.


Input: 4-20 mA @ 30 VDC maximum
Display: 1.0" (25.4 mm) LCD, 3½ digits; 1999
Accuracy: ±0.1% FS ±1 count
Approvals: FM Approved & CSA Certified as intrinsically safe with entity, for use in Class I, II, III, Division 1, Groups A, B, C, D, E, F, & G; T-code = T4; hazardous locations. Non-incendive for use in Class I, II, III, Division 2, Groups A, B, C, D, F, & G.
Entity Parameters: Vmax= 30 V, Imax = 175 mA, Ci= 0 µF, Li = 0 µH, Pi = 1.3 W
FM Approved: Intrinsically Safe, Class I Zone 0
See Control Drawing LIM686-2 for complete installation instructions.
Decimal Point: User selectable
Calibration: Two-step; non-interacting zero and span
Calibration Range: 4 mA input: -1000 to +1000;
20 mA input: between 20 and 2000 counts > 4 mA display
Display Update Rate: 2.5/second
Maximum Input Current: 30 mA
Maximum Voltage Drop: 1 V @ 20 mA
Operating Temperature: PD686: -40 to 85°C
for Canadian installations -40 to 40°C.
Storage Temperature: -40 to 85°C
Relative Humidity: 0 to 90% non-condensing. Printed circuit boards are conformally coated.
Enclosure: Impact-resistant glass filled polycarbonate body, color: gray; impact-resistant clear polycarbonate cover; NEMA 4X, IP67
Connections: Removable screw terminals accept 12 to 26 AWG
HART Transparency: Analog input will not interfere with existing HART communications on the wired 4-20 mA signal
Conduit Hole: One ½" conduit hole provided; refer to Ordering Information to specify conduit hole location; request models with rear conduit hole (-X) for panel mounting applications.
Weight: 12 oz (340 g)
Warranty: 2 years parts & labor


Figure 1: Calibrator Connected to Input Signal PCB

Figure 2: Control Loop Connected to Input Signal PCB

Figure 3: Calibrator Connected to Display PCB

Dimensions and Wall Mounting

A: 3.15" (80 mm)C: 2.36" (60 mm)E: 2.56" (65 mm)
B: 5.51" (140 mm)D: 4.72" (120 mm)F: 0.79" (20 mm)

Pipe Mounting Kit

The PDA6845 is a pipe mounting kit with two mounting holes. It provides all of the necessary hardware to mount the PD686 to a 2" pipe. It is available in zinc plated and stainless steel materials.

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.


Choose Your Options

Configurations other than those specified above are available at a $250 adder. Consult factory for desired model number and price.

Why you should buy: