ASHE JM-408 User manual

OPERATION MANUAL
DIGITAL LOOP POWERED INDICATOR
Model : JM-408

DIGITAL LOOP POWERED INDICATOR
JM-408
PRINCIPLE OF OPERATION
The Model JM-408 Digital process Indicator is a compact, rugged and reliable indicating instrument
which is specifically designed for accurate process measurement applications in areas without
power availability.
The Indicator accepts an industrial standard current input signal of 4 to 20 mA DC and displays the
actual process value calibrated in the desired units, on a linear scale. The process value is
displayed on a 4-Digit seven-segment red LED digital display module. There is no necessity of any
external Power Supply.
The instrument is fully configurable and can be calibrated on any scale range from  999 to +9999
units. Decimal Point setting is also provided in the instrument.
The principal of operation is briefly as follows :- The Input signal is passed through a series of
amplification and conditioning stages. Initially, the signal is conditioned internally and fed to a
signal convertor circuit. Thereafter, the transduced signal output of this convertor is fed into an A/D
Convertor before being finally passed through a Decoder/Driver digitizing circuit which displays the
input signal in the form of decimal digits on a seven-segment display module.
The field mounted unit has no potentiometers to adjust and all settings can be performed digitally
using only the three membrane switches that are available on the front panel. The NEMA4X rating
provides total immunity to corrosive atmospheres, high humidity (including condensation) and dust.
The JM-408 Indicator is therefore an ideal single unit substitute to conventional analog indicators
because of it’s easy set up procedure and inherent accuracy in process control, besides other
superior characteristics like immunity to Shocks, Dust, Ambient temperatures, Humidity and
Corrosive atmospheres. It’s main advantage is that it is completely current loop-driven, eliminating
the requirement of any external power supply source and associated cabling.
The instrument is manufactured using selected high-grade components which guarantee its
reliability and long operational parts. There are no moving parts and no potentiometers that may
drift over time and in high vibration applications.
INSTALLATION
The Model JM-408 is designed for field mounting in an Aluminum die-cast enclosure with IP65
ingress protection. The instrument should be first installed on the required panel face by means of
the two clamps provided for the same.
All inter-connections to the instrument should be made with strong multi-strand wire of the order of
2.5 sq.mm. The ends of the wires should be properly ferruled and suitable lugs must be used for
effective termination. The Cables carrying the Input Signal should be properly isolated from the
Power Line cables (even separate router channels), to prevent any electromagnetic interferences
in the Input Signal readings from disturbances in the Mains Power Line. There is no requirement of
power supply or earthing. It is recommended that the polarities of the input signal be double-
checked for correctness before energizing the instrument.

OPERATION
CONTROL KEYS
The instrument has three keys on the front panel, functions of which are described below :
The PROG or PROGRAM key is the central co-ordinating key to access the
settings of the instrument. Pressing this Key allows the operator to sequentially
view, change and save the parameters such as Zero and Span settings and
Decimal Point for the digital display.
The INC or Incrementing key allows the operator to select the numeral in the
digit being set. The digit will sequentially display 0, 1, 2….9 on each pressing of
the INC key. This may be used to set the calibration range of the instrument.
The DEC or Decrementing key allows the operator to select the numeral in the
digit being set. The digit will sequentially display 9, 8, 7….1 on each pressing of
the DEC key. This may be used to set the calibration range of the instrument.
SETTINGS
The following is the sequence of settings possible on the Digital Loop Indicator :
Since the input signal to the Loop Indicator is 4 to 20 mA DC, the
reference signal is internally generated for calibration. As such, no
external signal is required to be fed to the input terminals at the time of
calibration.
First, ensure that the terminations have been made as per the enclosed Terminal Diagram and the
input signal has been connected at the terminals in the correct polarity. On energizing the input
signal, the digital display will immediately indicate the actual process value. (For calibration details
of the Indicator, please refer to the Technical Specifications).
The scale calibration can be changed whenever required with the help of the three-key Membrane
Keyboard on the front panel. The Decimal position also may be selected by using the keyboard
(see Calibration section). However, it is strongly recommended that only authorized personnel
should attempt any alterations or rectifications in the instrument.
All settings and adjustments must be done from the three-key Membrane Keypad on the front
panel of the module.
CONNECTIONS
 Locate the two-way terminals on the rear of the module.
 Connect the analog current loop input signal of 4 to 20 mA at the terminals in the indicated
polarity.
PROG
INC
DEC

PROGRAMMING INSTRUCTIONS
CALIBRATION
(Note: Bold Text indicates flashing)
KEY
PRESSED
DISPLAY
FUNCTION
(POWER
ON)
Process Mode
Actual process value
PRESS

TOGETHER
FOR 2 SEC
t–LO
Internal Factory Setting
(not for customer Use)
PROG
P
t–hi
Internal Factory Setting
(not for customer Use)
PROG
P
r n G L
Range Low Setting
Use  and  keys
PROG
P
r n G H
Range High Setting
Use  and  keys
PROG
P
d P
Decimal Point Setting
Use  and  keys
PROG
P
––––
Saving of settings and re-initialisation
Process Mode
This completes the entire settings of the Loop Powered Digital Indicator. (Note: All parameters to
be shifted/selected using INC and DEC keys).

TECHNICAL SPECIFICATIONS
Model : JM-408
Type : Digital Loop-powered Indicator.
Input Signal : 4 to 20 mA DC.
System : Two-wire.
Indication : 4 digit seven-segment LED display.
Display height : 0.5”.
Forward Voltage Drop : 3.0 Volts @ 20 mA.
Sensing Resistance : 3.30 Ohms.
Range : 0.0 to 100.0
Calibration Range : As per required (Configurable).
Under-Range indication : Indication of “Err” on display.
Over-Range indication : Indication of “Err” on display.
Polarity : Auto-Sensing.
Calibration : By three-key Membrane Keypad.
Power Supply : Nil (Loop-powered).
Settings : Zero, Span, Decimal point.
Response time : Typically 20 mS.
Linearity :  0.1% FS.
Resolution :  0.1%,  1 digit.
Ambient temperature : 0 to 50
O
C.
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