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简单介绍：
We packaged our most popular PD138 product combination for you at a significant savings vs. buying these components separately. The PDS178 is a kit that includes a PD765-6R2-00 Trident and PD138 MINIM
详情介绍：
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SCAN MOST SIGNALS/SENSORSThe Watchdog Temperature Scanning & Alarm System brings together a popular combination of Precision Digital products: the Trident meter, the Minimux II Scanner, and a PDA2821 NEMA 4X enclosure.The scanner provides low-cost automatic switching for multipoint display and alarms. Signal switching is done via reed relays making the Watchdog (as configured) ideal for switching up to eight thermocouple or RTD inputs. The Watchdog can be used in a variety of temperature monitoring applications. A very common application for this system is to monitor bearing temperatures (as shown above). Because of the popularity of this combination, we can offer this system at a price significantly below what it would cost to buy these components separately. APPLICATIONUsing the PDS178 to scan ThermocouplesIn the following application example, four oven thermocouples are scanned and channeled to a PD765 Temperature Meter where the PV is displayed and checked for low or high alarm conditions. All four ovens share the same low and high alarms, so the alarm inputs are joined together on the PD138The PD138 MINIMUX II is programmed in the following manner to satisfy this application:
 The Minimux II switches to (scans) input 2, channeling it to the PD765-6R2-00 where a temperature of 345° triggers a high alarm condition. The PD138 is programmed for Sequence A, so the channel 2 LED alternately flashes yellow and green, the internal horn sounds, and the PD138’s alarm relay transfers causing an external horn to sound. After acknowledging the alarm the channel LED will glow a steady yellow (while selected), or steady red (when not selected) until reset.  The Minimux II switches to (scans) input 3, channeling it to the PD765-6R2-00 where a temperature of 220° is found to cause a low alarm condition 2 seconds into the dwell time. Channel 3 LED alternately flashes yellow and green (shown yellow), the internal horn sounds and the PD138's alarm relay transfers causing an external horn to sound. SIGNAL CONNECTIONS
Thermocouple InputsThe example shown below has 3 type J thermocouples multiplexed by the PD138 into the PD765. Thermocouple wire must also be used between the PD138 and the PD765. The PD765 also accepts 100 Ω Platinum RTD sensors and process inputs.SPECIFICATIONSExcept where noted all specifications apply to operation at +25°CThe partial list of specifications shown below are key to the PDS178 system. For complete specifications on both the PD138 Minimux II and the PD765 Trident, see the listed Documentation for more information. Input Channels: Up to 8 channels Signal Switching: DPST relays Contact Resistance: 0.2 Ω maximum Dwell Time: Each channel adjustable from 0.6 to 30 seconds Scan Stop: Hold STOP/GO button for 0.5 seconds Alarm Acknowledge: Front panel ACK button Alarm Output: Relay, 1 SPDT rated 2 Amp @ 30 VDC or 250 VAC Temperature Inputs: J, K, E, T thermocouples, 100 Ω platinum RTD Digital Display: 0.56" (14 mm) high, red LED, 4 digits Accuracy: Temperature ±1°C/±2°F, Process ±0.05% of span ±1count Operating Temperature: 0 to 65°C Storage Temperature: -40 to 85°C Power: 115 VAC, ±10%, 50/60 Hz, 22 W max Compliance: NEMA 4X Enclosure Dimensions: 7.38" x 11.00" x 7.13" (H x W x D) |
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