DMS-40LCD-4/20S 4½ DIGIT, 4-20mA INPUT, LOOP-POWERED LCD DISPLAY METERS
D
A
TEL,
Inc.,
Mansfield,
MA
02048
(USA)
•Tel:(508)339-3000, (800)233-2765 Fax:(508)339-6356 • E-mail:[email protected] • Internet:www.datel.com2
Performance/Functional Specifications
TypicalatTA= +25°C, unlessotherwise noted.
Technical Notes
(1) Full Scale Input:The Display readings shown inTable 1 can typically be
obtainedwith transmitters havinga low-level output of 3.8to 4.3mA anda
full-scaleoutput of 19.4to 20.4mA. Whenusing atransmitter whose
outputfallsoutsidethese ranges and thedesireddisplayreadingsare
closeto the upper or lower adjustment limits of the selected DIP-switch
setting #, try using the next highest DIP-switch setting # if, after
adjustingR7, thedisplayreading is still too low, orthe nextlowestsetting
# if thedisplay reading isstilltoo high (see examplenumber2). Please
keepin mind thatthe DMS-40LCD meter from whichthe DMS-40LCD-
4/20Sis derivedhas anaccuracy specification of ±3 counts (max.); thus,
itmay not alwaysbe possibleto obtain theexact desireddisplay
readings.A change of±1 count isdefined as theright-hand most digit
goingupordownbyone.
Displayreadings other thanthoseshowninTable1 are obtainable.For
example,somenegativereadings with a4mAinputare possible. Consult
DATELfor moreinformationregarding displayreadings not showninthe
table.
(2) Max.Loop-Voltage Drop/Max.Loop impedance:The maximum loop
voltage-dropand maximum loop impedance(burden)arebothspecified
withthe meter configuredfor DIP-Switch setting#20 andan input loop
currentof 20.0mA.
(3)Temperature Drift:Temperaturedriftofzeroand temperature driftofgain
areboth specified withthe meter configuredfor range #20with a 4mA
inputadjusted(using R3) toread “0000”±1 count, anda 20mA input
adjusted(usingR7) to read“19000”±2countsat an initial ambient
temperatureof25°C.
Operating and Setup Instructions
The following procedure must be performed as the first re-calibration
step every time DIP-switches S1 and S2 are reconfigured to select a
new display range.The following procedure assumes the DMS-40LCD-
4/20S is initially completely mis-adjusted, i.e., both potentiometers and
DIP-switches S1 and S2 are randomly set. Make sure that all DIP-switch
actuators are pushed as far as they will go to their designated ON
(closed) or OFF (open) positions.
The temperature drift of gain is proportional to the selected full-scale
range. It is typically less pronounced at the lower range settings, that
is, if the observed gain drift of a particular meter is +12 counts when
reading “19000”on range #20 at 40°C, the same meter will most
likely have a drift of only +6 counts when reading “9000”on range
#12 at 40°C.
The normally very accurate, temperature-insensitive autozero feature
of the DMS-40LCD-4/20S’s built-in analog-to-digital converter (A/D)
is not a significant factor in determining the meter’s overall zero-
reading stability over its rated operating temperature because an
offset voltage is applied to the A/D’s LO input.This offset is used to
null the signal voltage developed with a 4ma input. In order for the
A/D to display a steady “0000”±1 digit, the autozero circuitry requires
both A/D inputs to always be at exactly zero volts.
The meter’s zero-reading stability over its specified operating
temperature is affected by the drift of three terms: the voltage
developed by the meter’s offset circuitry;the voltage developed
across the meter’s input resistors with a 4mA input;and the stability of
the applied 4mA input signal itself. In the lower DIP-switch settings
(ranges #1-4), the meter’s parasitic etch and switch impedances also
contribute a small error voltage.
The meter’s performance with regards to span stability over
temperature is affected by the drift of the meter’s gain circuitry and
loop input-resistors.To minimize these drifts in applications requiring
the utmost in temperature stability, where possible, the meter should
be calibrated at its anticipated operating temperature.
Since the DMS-40LCD-4/20S uses extremely-stable thin-film chip
resistors, periodic re-calibration is typically required only in
environmentally demanding applications where shock, vibration,
and/or temperature extremes may have a detrimental effect on the
20-turnpotentiometers.
Switch S2
SW3 SW4 SW5 SW6
DP1 DP2 DP3 DP4
Decimal Point Settings
Using the chart below as a guide, the DMS-40LCD-4/20S’s decimal
points can be configured to suit the user’s particular readout
requirements.To enable a desired decimal point place its DIP switch
to the ON position (up). Please note that the decimal points are
merely placeholders, that is, they can all be on or all off; they do not
affect the meter’s operation and/or display readings.
Current Loop Input Min. Typ. Max. Units
Full Scale Input Range
(1)
+3.8 —+20.4 mA
Loop Impedance
(2)
——190 Ohms
Voltage Drop
(2)
—2.9 3.8 Volts
Overcurrent Protection ——±40 mA
Performance
Sampling Rate 2.5readings per second
Adjustable Accuracy (5 min. warm-up) ±0.01%of full scale ±2 counts
Temperature Drift of Span
(3)
—±0.3 ±0.6 Cnts/°C
Temperature Drift of Zero
(3)
—±0.2 ±0.5 Cnts/°C
Display
DisplayType and Size 4½digit LCD, 0.40"/10.2mm high
Polarity Indication "-" for negative readings
Overrange Indication "1----"
Physical/Environmental
OperatingTemperature 0—+50 °C
StorageTemperature –20 —+75 °C
Humidity (Non-condensing) 0—95 %
Case Material Polycarbonate
Weight 1 ounce (28grams)
