Dwyer Instruments A-705-20 User manual

Bulletin A-30-705
A-705-20 LOOP CURRENT METER
Specifications - Installation and Operating Instructions
DWYER INSTRUMENTS, INC. Phone: [phone] www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, IN 46361, U.S.A. Fax: [phone] e-mail: [e-mail]
UNIT DESCRIPTION
The A-705-20 digital panel meter is a dual range, unipolar, 3 1/2 digit, LCD
current meter. It is powered by the current loop being measured and has
selectable full scale ranges of 4-20mA and 10-50mA. This unit is designed
with a small case size and easy calibration from the right side of the meter.
MODEL NUMBER RANGE
A-705-20 4-20mA
A-30-705 6/22/05 2:43 PM Page 1

2
TABLE OF CONTENTS
Common Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Installation
Mechanical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Panel Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
DPM Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Connections and Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical Connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electronic Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 -10
Schematic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
LIST OF TABLES
Decimal Point Location 1.XXX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Decimal Point Location 1X.XX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Decimal Point Location 1XX.X. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Decimal Point Location 1XXX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
LIST OF FIGURES
DPM Dimensions & Panel Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
DPM Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Meter rear Pinout Location. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Headers & Jumpers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electronic Assembly (Front) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Electronic Assembly (Back) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Electronic Schematic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A-30-705 6/22/05 2:43 PM Page 2

3
SPECIFICATIONS
•Power requirements–– None Required Power is derived from current
source being monitoring with a voltage drop of less than 3.2V(with a
20mA input)
•Range–– ±1999
•Accuracy–– ±0.1% Rdg., ± 1digit
•Settling Time–– Under 1 sec. typical
•Operating Temperature–– 0°C to +50°C
•Storage–– -20°C to +70°C, 72 hrs., -10°C to +60°C, Indefinite.
•Humidity–– 80% RH @ 40°C max., 70% RH @ 50°C max.
•Decimal Points–– set by internal jumper, 1.XXX, 1X.XX, 1XX.X, 1XXX.
•Polarity–– negative count; minus sign at left, positive count, plus sign at
left.
•Tempco–– 100ppm/°C typical
•Weight–– approx. 2 oz.
•Display–– 0.6˝ high LCD
•Recalibration Schedule–– 1 yr. within rated accuracy
•Overrange Indication–– Positive overrange; Negative overrange; -1;
other digits blank.
•Size–– See outline dimensions.
A-30-705 6/22/05 2:43 PM Page 3

4
Installation
Mechanical Installation
The figure below shows a pictorial view and overall dimensions.
Panel Preparation
Prepare a panel cut-out as shown below at the desired location
A-30-705 6/22/05 2:43 PM Page 4

5
DPM Installation
•Insert meter in panel cutout from the front.
•From rear, place short side of mounting clips in slots at top and bottom of case. Face
short side of clips to rear.
•Thread the screws into the clips and tighten against panel.
If it is necessary to remove lens, grasp the sides of the meter and press in until lens
bows out. Pull out lens at center.
NOTE: Shorting BC6 will change the function of J-5 to “loop - (50mA)”. This allows the
option of switching the meter between 4-20mA and 10-50mA with a jumper rather than
rewiring the installation see page 10 for reference.
CONNECTIONS AND
CONFIGURATION
Electrical Connections
The model A-705-20 accepts a 10 pin mating connector at the rear for decimal point and
signal inputs. The figure below shows the pinout configuration and the location on the rear
of the meter.
OPERATION
Signal Inputs: apply between pin 2 (Hi) and pin 5 (Lo 20mA) or pin 4 (Lo 50mA).
Decimal Point Selection: activation requires the placement of a jumper from J1 pin
7 to pin 6 from J1 pin 8 to pin 9 (or pin 7), or from J1 pin 10 to pin 9. The factory
setting is for a 20mA meter with selection of 1X.XX. To use other selections,
remove jumper and reinstall on the appropriate pin combination for the decimal
A-30-705 6/22/05 2:43 PM Page 5

6
CALIBRATION
Allow 5 minutes warm-up with signal of 20mA. The number displayed on the A-705-20
readout is determined by the equation: D = S * I + O where “D” is the count being dis-
played, “S” is a constant scale factor having the dimensions of counts per milliampere, “O”
is a constant scale factor having the dimensions of counts, and “I” is the input current to
the A-705-20.
Example:
Consider the case in which inputs of 4mA and 20mA yield displays of 000 and 100 respec-
tively. Solving the equation for “S” and “O” gives
Where IHis the higher value of current input in milliamperes
ILis the lower value of current input in milliamperes
DHis the display value corresponding to IH
DLis the display value corresponding to IL
Substituting in the equation for “O” gives: “O”= 000 - 6.25 x 4 = -25 counts
The basic equation for the volume displayed is D = 6.25 I - 25.9
After the value for “S” and “O” have found, the A-705-20 can be programmed to respond
in accordance with the basic equation. Programming involves placing two of four internal
jumpers. NOTE: first the decimal point location must be determined. For the example
above, we will choose a decimal point location of 1XX.X. The decimal point location in the
following tables has been adjusted accordingly.
Since “S” in the example (6.25) falls in the range 5.2 to 8.8, both BC1 and BC2 should be
open.
The settings of BC4 and BC5 depend on the value of O and the ranges of O are listed in
the table below.
“S” In Counts/mA
0 to 5.7
6.2 to 8.8
8.3 to 14.0
BC1
Shorted
Open
Open
BC2
Open
Open
Shorted
Scale = Display High - Display Low
Input High - Input Low “S” = 100 - 000 20 -4 = 6.25 counts per mA
S = DH- DL
IH- IL
O = DL- (S • IL)
A-30-705 6/22/05 2:43 PM Page 6

7
O (offset) in Counts
+199.9 to 57.9
+61.6 to -60.8
-56.5 to -199.9
BC4
Shorted
Open
Open
BC5
Open
Open
Shorted
Since O in the example (-25.0) falls in the range +61.6 to -60.8, both BC4 and BC5 should
be open.
After BC1 , 2, 4, and 5 have been set, the potentiometers R9 and R12 (behind the front
panel) need to be recalibrated for an accurate reading. The procedure is as follows:
1. Connect the positive input lead (current going into the meter) from a current stan-
dard to Pin2 of J1 at the rear of the meter. The negative lead attached to pin 5 of
J1.
2. Short BC3 in the “O” position.
3. Adjust the current standard to approximately ten milliamperes (the value is not crit-
ical for this step).
4. Adjust R9 until the display shows the correct offset value (“O”). (-25.0 in the exam-
ple).
5. Move BC3 jumper to the “S” position.
6. Set the current standard to 10mA.
7. Adjust R12 until the display shows the correct scale factor value X 10. (6.25 X 10
= 62.5 for the example).
8. Remove the BC3 jumper.
9. Verify that the display shows the correct value for 4mA & 20mA inputs (000 &
100.0 respectively for the example).
The following four sets of tables are for the different decimal point location as noted.
“S” In Counts/mA
0 to .057
.052 to .088
.083 to .140
BC1
Shorted
Open
Open
BC2
Open
Open
Shorted
DECIMAL POINT LOCATION 1.XXX (JUMPER J1 PIN 9 TO J1 PIN 10)
O (offset) In Counts
+1.999 to +.579
+.616 to -.608
-.565 to -1.999
BC4
Shorted
Open
Open
BC5
Open
Open
Shorted
DECIMAL POINT LOCATION 1.XXX (JUMPER J1 PIN 9 TO J1 PIN 10)
A-30-705 6/22/05 2:43 PM Page 7

8
“S” In Counts/mA
0 to .57
.52 to .88
.83 to 1.40
BC1
Shorted
Open
Open
BC2
Open
Open
Shorted
DECIMAL POINT LOCATION 1X.XX (JUMPER J1 PIN 8 TO J1 PIN 7 OR 9)
O (offset) In Counts
+19.99 to +5.79
+.616 to -.608
-5.65 to -19.99
BC4
Shorted
Open
Open
BC5
Open
Open
Shorted
DECIMAL POINT LOCATION 1X.XX (JUMPER J1 PIN 8 TO J1 PIN 7 OR 9)
“S” In Counts/mA
0 to 5.7
5.2 to 8.8
8.3 to 14.0
BC1
Shorted
Open
Open
BC2
Open
Open
Shorted
DECIMAL POINT LOCATION 1XX.X (JUMPER J1 PIN 6 TO J1 PIN 7)
O (offset) In Counts
+199.9 to +57.9
+61.6 to -60.8
-56.5 to -199.9
BC4
Shorted
Open
Open
BC5
Open
Open
Shorted
DECIMAL POINT LOCATION 1XX.X (JUMPER J1 PIN 6 TO J1 PIN 7)
A-30-705 6/22/05 2:43 PM Page 8

9
“S” In Counts/mA
0 to 57
52 to 88
83 to 140
BC1
Shorted
Open
Open
BC2
Open
Open
Shorted
DECIMAL POINT LOCATION 1XXX (NO JUMPERS)
O (offset) In Counts
+1999 to +579
+616 to -608
-565 to -1999
BC4
Shorted
Open
Open
BC5
Open
Open
Shorted
DECIMAL POINT LOCATION 1XXX (NO JUMPERS)
A-30-705 6/22/05 2:43 PM Page 9

10
A-30-705 6/22/05 2:43 PM Page 10