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DMS-40LCD-4/20S Series

Ultra-Low 2.9V Loop-Drop 4½ Digit

LCD Display Process Monitor

MPM_DMS401LCD-420S.D02 Page 2 of 5

TECHNICAL NOTES

DECIMAL POINT SETTINGS

Performance/Functional Specifications

(1) Full Scale Input: The Display readings shown in Table 1 can typically

be obtained with transmitters having a low-level output of 3.8 to 4.3mA

and a full-scale output of 19.4 to 20.4mA. When using a transmitter

whose output falls outside these ranges and the desired display read-

ings are close to the upper or lower adjustment limits of the selected

DIP-switch setting #, try using the next highest DIP-switch setting #

if, after adjusting R7, the display reading is still too low, or the next

lowest setting # if the display reading is still too high (see example

number 2). Please keep in mind that the DMS-40LCD meter from

which the DMS-40LCD-4/20S is derived has an accuracy specification

of ±3 counts (max.); thus, it may not always be possible to obtain the

exact desired display readings. A change of ±1 count is defined as the

right-hand most digit going up or down by one.

DMS-40LCD-4/20S

4½ digit, LCD, loop-powered meter

DMS-BZL1

Panel-mount bezel assembly

DMS-BZL2

Panel-mount bezel assembly with

sealing gasket

DMS-30-CP

Panel cutout punch

A panel-mount retaining clip is supplied with each meter.

Display readings other than those shown in Table 1 are obtainable.

For example, some negative readings with a 4mA input are possible.

Consult DATEL for more information regarding display readings not

shown in the table.

(2) Max. Loop-Voltage Drop/Max. Loop impedance: The maximum loop

voltage-drop and maximum loop impedance (burden) are both speci-

fied with the meter configured for DIP-Switch setting #20 and an input

loop current of 20.0mA.

(3) Temperature Drift: Temperature drift of zero and temperature drift of

gain are both specified with the meter configured for range #20 with a

4mA input adjusted (using R3) to read “0000” ±1 count, and a 20mA

input adjusted (using R7) to read “19000” ±2 counts at an initial ambi-

ent temperature of 25°C.

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-turn potentiometers.

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 Burden (2)

–

–

190

Ohms

Voltage Drop (2)

–

2.9

3.8

Volts

Overcurrent Protection

–

–

±40

mA

Performance

Sampling Rate

2.5 reading per second

Accuracy (1 minute warm-up)

±0.05%FS ±1 Count

Temperature Drift of Span (3)

–

±0.3

±0.6

Cnts/°C

Temperature Drift of Zero (3)

–

±0.2

±0.5

Cnts/°C

Display

Display Type and Size

4½ digit, 0.4"/10.2mm high LCD

Polarity Indication

"–" for negative readings

Overrange Indication

"–1_ _ _ " for negative inputs

"1_ _ _ " for positive inputs

Physical/Environmental

Operating Temperature

0

–

+50

°C

Storage Temperature

–20

–

+75

°C

Humidity (non-condensing)

0–

95

°C

Case Material

Polycarbonate

Weight

0.1 ounces (28 grams)

Ordering Information