Datel DMS-40LCD-4/20S Handbuch - Seite 2

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DMS-40LCD-4/20S

Performance/Functional Specifications

Typical at T

= +25°C, unless otherwise noted.

Current Loop Input

Full Scale Input Range (1)

Loop Impedance (2)

Voltage Drop (2)

Overcurrent Protection

Performance

Sampling Rate

Adjustable Accuracy (5 min. warm-up)

Temperature Drift of Span (3)

Temperature Drift of Zero (3)

Display

Display Type and Size

Polarity Indication

Overrange Indication

Physical/Environmental

Operating Temperature

Storage Temperature

Humidity (Non-condensing)

Case Material

Weight

Technical Notes

(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 readings 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 thedisplay 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.

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 specified

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 ambient

temperature of 25°C.

DATEL, Inc., Mansfield, MA 02048 (USA) • Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356 • E-mail: [email protected] • Internet: www.datel.com

4 ½ D I G I T , 4 - 2 0 m A I N P U T , L O O P - P O W E R E D L C D D I S P L A Y M E T E R S

Min.

Typ.

Max.

Units

+3.8

—

+20.4

—

190

Ohms

—

2.9

3.8

Volts

—

±40

2.5 readings per second

±0.01% of full scale ±2 counts

—

±0.3

±0.6

Cnts/°C

—

±0.2

±0.5

Cnts/°C

4½ digit LCD, 0.40"/10.2mm high

"-" for negative readings

"1----"

—

+50

–20

—

+75

—

Polycarbonate

1 ounce (28grams)

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

°C

(ranges #1-4), the meter's parasitic etch and switch impedances also

°C

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.

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.

SW3

DP1

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.

Switch S2

SW4

SW5

DP2

DP3

SW6

DP4