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PD688 Loop Leader Loop-Powered Intrinsically Safe & Nonincendive Digital Panel Meter

USA Toll Free: 1-800-730-0302 Tel: 416-240-1920 -

The Loop Leader PD688 is an Intrinsically Safe and Nonincendive, loop-powered, 1/8 DIN digital panel meter designed for hazardous process control applications. 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. The PD688 loop-powered indicator is built in a shallow-depth case with an FM Type 4X front and features loop-powered backlighting and a wide -30 to 65°C operating temperature range. It doesn't matter if it's indoors or outdoors, in bright sunlight or a dimly lit plant, or in an area that is wet, dirty, hot, or cold, the Loop Leader can go just about anywhere. The PD688 can be installed in just about any hazardous area environment under the FM, CSA, and ATEX standards.


  • 4-20 mA Input
  • 5-Digit Display
  • 0.6" (15.2 mm) LCD
  • FM Type 4X, IP65 Front
  • Shallow Depth Case 3.2" Behind Panel
  • 2 V Drop (5.7 V with Backlight)
  • Loop-Powered Backlight
  • Custom Engineering Units
  • Bargraph Display & Trend Arrow
  • Maximum & Minimum Display
  • Square Root, or Programmable Exponent
  • Non-Volatile Memory - No Battery Needed
  • Operating Temperature Range: -30 to 65°C
  • Intrinsically Safe & Non-Incendive
  • CE, ATEX, FM, and CSA Certified
  • HART Protocol Transparent

PD688 Loop Leader Loop-Powered Intrinsically Safe & Nonincendive Digital Panel Meter Data Sheet
PD688 Loop Leader Loop-Powered Intrinsically Safe & Nonincendive Digital Panel Meter Instruction Manual

General Specifications

  • Display: Five digits: -99999 to 99999, 0.60" (15.2 mm) high, 7-segment, automatic lead zero blanking.
  • Engineering Units: 0.25" (6.4 mm) high, 14-segment.
  • Bargraph: 20-segment, 0% to 100% indication.
  • Trend arrows: Up and down trend indication.
  • Backlight: Bright orange (intensity varies with signal)
  • Display Update Rate: 2.5/second
  • Overrange: Display flashes 99999
  • Underrange: Display flashes -99999
  • Programming Method: Four front panel buttons
  • Noise Filter: Programmable from 1 to 199
  • Recalibration: Recommended at least every 12 months.
  • Max/Min Display: Max/min readings reached by the process are stored until reset by the user or until power to the meter is turned off.
  • Password: Programmable password restricts modification of programmed settings.
  • Non-volatile Memory: All programmed settings are stored in non-volatile memory for a minimum of ten years if power is lost.
  • Voltage Drop: 2.0 V max w/o backlight, 5.7 V max with backlight
  • Equivalent Resistance: 125 O @ 20 mA w/o backlight, 315 O @ 20 mA with backlight
  • Normal Mode Rejection: 64 dB at 50/60 Hz
  • Operating temperature range: -30 to 65°C
  • Allowable Temperature Range: -40 to 65°C* (see note below)
  • Storage temperature range: -40 to 65°C
  • Relative humidity: 0 to 90% non-condensing
  • Connections: Screw terminals accept 12 to 22 AWG wire
  • Enclosure: 1/8 DIN, high impact plastic, UL 94V-0, color: gray
  • Mounting: 1/8 DIN panel cutout required. Two panel mounting bracket assemblies provided
  • Tightening Torque: 4.5 lb-in (0.5 Nm) Screw terminal connections
  • Overall Dimensions: 2.45" x 4.68" x 4.19" (62 x 119 x 106 mm)
  • Weight: 5.7 oz (162 g)
  • Warranty: 3 years parts & labor


  • Input Range: 4-20 mA
  • Accuracy: ±0.03% of span ±1 count, square root and programmable exponent: 10-100% FS
  • Calibration: Scale without signal or calibrate with signal source
  • Calibration Range: User programmable over entire range of meter
  • Minimum Span: 0.40 mA between input 1 and input 2
    Note: An Error message will appear if input 1 and input 2 signals are too close together
  • Input Overload: Over current protection to 2 A max.
  • HART Transparency: Analog input will not interfere with existing HART communications on the wired 4-20 mA signal
  • Decimal Point: Up to four decimal places (d.dddd, dd.ddd, ddd.dd, dddd.d, or ddddd)
  • Function: Linear, square root, or programmable exponent
  • Low-Flow Cutoff: -99999 to 99999 (-99999 disables cutoff function)
  • Temperature Drift: 50 PPM/°C from -40 to 65°C ambient
    *Below -30°C the LCD becomes less readable.

PD688 Approvals for Hazardous Locations

FM Approved & CSA Certified as intrinsically safe with entity for use in Class I, Div 1, Groups ABCD; Class II, Div 1, Groups EFG; Class III, Div 1; Class I, Zone 0, Group IIC; T-code = T4. Non-incendive: Suitable for use in Class I, Div 2, Groups ABCD; Class II, Div 2, Groups FG; Class III, Div 2.
Entity Parameters: Ui: 30 V; Ii: 175 mA; Ci: 0; Li: 0; Pi: 1.0 W

ATEX II 1G, Ex ia IIC T4, IP65, Ta = -40°C to 65°C

Note: Installation must be performed in accordance with Control Drawing LIM688-2

The Information contained in this document is subject to change without notice. Precision Digital Corporation makes no representations or warranties with respect to the contents hereof, and specifically disclaims any implied warranties of merchantability or fitness for a particular purpose.


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Metex Corporation Limited has been providing superior products and services to the process control, chemical treatment, waste water, industrial and manufacturing industries for over 25 years. It is our goal to continually provide our customers with the best possible equipment, technology, and service.


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