Datasheet DMS-20PC (Murata) - 3

DMS-20PC Series
3½ Digit, LED Display, Low-Cost, Subminiature Digital Panel Voltmeters
4. DISPLAY TEST/HOLD (Pin 9) Function
: Pin 9 is a dual-function
8. Suggested Mating Connectors:
pin. On all standard models (without "-H" suffi x), tying pin 9 to pin 1
Panel mounted:
(+5V SUPPLY) activates the meter's DISPLAY TEST feature. All display Connector housing Murata Power Solutions P/N 4320-01069-0 segments, except the decimal points, will be illuminated. The display Terminal type Murata Power Solutions P/N 4400-01032-0 will show "1888" ("–1888" if a negative input signal is present). Do Crimping tool Murata Power Solutions P/N 39-2099000 not leave the meter in the test mode for more than 10 seconds as this will cause the meter's operating temperature to rise and possibly Wire size 22 to 26 AWG affect its performance. Pin 9 must be left open when the test function Insulation diameter 0.062" (1.57mm) maximum is not being used. Stripping length 0.100 to 0.125" (2.54 to 3.17mm)
Board mounted:
On models with the "-H" suffi x (DMS-20PC-1-RS-H for example), pin Socket Murata Power Solutions P/N 4320-01074-0 9 serves as a DISPLAY HOLD control pin. Tying pin 9 to +5V SUPPLY (pin 1) on these models will hold or "freeze" the current display read- ing indefi nitely. Pin 9 must also be left open when the hold function is
APPLICATIONS
not being used. After disabling DISPLAY HOLD, allow the meter a full DMS-20PC meters are highly versatile devices that can be used in 10 seconds to resume normal calibrated operation before holding a hundreds of applications. The application circuits chosen for this section new reading. are ones that have historically received many inquiries. The DISPLAY TEST or DISPLAY HOLD pin should normally be con- The schematic in Figure 1 shows that the meter's high-impedance input nected, via a selector switch, to pin 1 (+5V SUPPLY). If automatic, consists of an op amp powered from a ±5Vdc power supply (the –5V is logic-controlled operation is desired, only PNP or MOSFET transis- internally generated). One can easily see why input signals applied to (–) tors should be used. The base or gate of these transistors should be INPUT LO and (+) INPUT HI have to be kept within the power supply rails driven suffi ciently hard to bring pin 9 within 0.05V of +5V SUPPLY. of ±5V. Also note that only pin 11 has a current-limiting 909kΩ series
5. DISPLAY ENABLE (Pin 2) Function
: On all models, tying pin 2 to resistor. High input voltages that have a common ground with pin 3 (5V pin 1 (+5V SUPPLY) applies full power to the LED display. This is the RETURN) should only be applied to pin 11 ((+) INPUT HI) and never to pin normal mode of operating the meter. Leaving DISPLAY ENABLE open 12. In these high-voltage cases, pin 12 should always be tied to pin 3 (no connection), only turns off the LED display. The meter's analog- (5V RETURN). to-digital converter continues to sample the input signal. Total current The schematic also shows that pin 3 is the meter's zero-volt reference consumption with the display off is approximately 400μA (0.4mA). point — regardless of the type of power or signal source used. This is This is a very useful feature if the meter is used in battery-powered an important point to keep in mind when a digital or analog multimeter equipment. is used to make system measurements. The multimeter's negative lead With the exception of the low-power red LED models (DMS-20PC-X- (usually the black one) must be connected to pin 3 (5V RETURN). RL), a regulated voltage lower than +5V SUPPLY can be used to dim the display intensity. Display intensity control is best performed with
1. Single-Ended Input Confi gurations
: True single-ended measure- the high brightness, red LED, DMS-20PC-X-RH model. All low-power ments can be made with any DMS-20PC meter. The circuit of Figure red LED models must have DISPLAY ENABLE tied directly to pin 1 2 avoids problems normally associated with ground-loop currents. (+5V SUPPLY). Voltages applied to DISPLAY ENABLE must never be Separate ground runs should be used for 5V RETURN (pin 3) and (–) greater than +5V SUPPLY. INPUT LO (pin 12).
6. Gain Adjust
: There is a gain-adjust potentiometer on the back of each meter. It has approximately ±50 counts (±2.5%) range of
DMS-20PC-1
adjustment. Since these devices essentially have no zero/offset
11 8
errors, a gain adjustment is effectively an overall accuracy adjust-
(+) IN HI REF OUT +
ment. Though they may be performed at any point (except zero),
VIN
accuracy adjustments are most effective when performed with higher level input signals. The circuit shown in Figure 10 provides
– 12 7
±10% range of adjustment.
(–) IN LO REF IN 7. Soldering Methods
: All models in the DMS-20PC Series easily with-
1 2 6 3
stand most common wave soldering operations. We recommend,
+5V SUP DISPLAY DP1 5V RET ENABLE
however, that you evaluate the effects your particular soldering techniques may have on the meter’s plastic case and high-precision
85-264Vac
electrical performance. We recommend the use of no-clean solders.
AC to DC Converter Figure 2.
Single-Ended Input Confi guration
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