Option F3A - Non-Isolated Parellel BCD Upper Board Three State with 1-Bit Enable

NON-ISOLATED PARALLEL BCD UPPER BOARD, THREE-STATE WITH 1-BIT ENABLE
OPTION F3A

FEATURES

Buffered

Stored

Three-state

Single-line enable

APPLICABLE INSTRUMENTS

Model 203A for DC signals

Models 204B, 2003B and 2004 for DC, AC, true-RMS or process signals

Models 267B and 268 for thermocouple or RTD temperature signals

The F3A is an upper-board option which provides buffered, stored, three-state parallel BCD output plus an enable line for addressing in data busing applications. BCD ground is tied to meter ground, so that the F3A can be powered by the host panel meter, without need for a separate power supply. The seven panel meters which accept the F3A option also provide a separate non-buffered, non-isolated parallel BCD output, which is a standard feature of the main board.

Buffering the output allows the F3A to drive one TTL load without affecting correct operation of the host panel meter.

Storing the BCD data assures that correct BCD data is always available, regardless of the current state of A/D conversion.

Three-state drivers allow all output lines to be put in a logical "0", logical "1", or high-impedance state. The high-impedance state does not load down the external circuit and allows multiple F3A's to be bused with all BCD lines in parallel.

NON-ISOLATED BCD CIRCUIT
The BCD ground of the F3A is tied to meter ground, so that ground loops may create reading errors in case of long line lengths in electrically noisy industrial environments. Ground loops will not occur and the F3A can safely be used if any of the following conditions are met:

1) The source of the analog signal is electrically floating. This is normally the case with RTD's and strain gauges.

2) The analog input to the meter is isolated. This is the case with all versions of Model 267B temperature meter and Model 204B with OI optically isolated input option.

3) The input to the BCD receiver is electrically floating with respect to power ground. This is the case with most AC-powered receivers, such as Newport's Model 820A printer, Model 872A setpoint controller, and Model 6152A 5-digit remote display. If ground loops are unavoidable with the non-isolated F3A, the isolated F4A should be used instead. The F4A also has more drive capability than the F3A, 12 TTL unit loads as opposed to 1 TTL unit load.

SEPARATE BCD HOLD AND METER HOLD
The F3A provides separate BCD and meter HOLD functions. In F3A BCD HOLD, the display and the standard BCD output of the main board continue to update while the BCD output of the F3A remains latched. Thus, the standard BCD output of the main board can be used as an uninterruped input to a Model 872A dual-setpoint controller while the BCD output of the F3A is on HOLD.

ENABLE-LINE ADDRESSING
The F3A provides an enable line, which can take the BCD output drivers out of the high-impedance state. This line allows a specific panel meter on a BCD bus to be selected by a programmable controller using simple single-line addressing. As a failsafe feature, an open enable line will automatically return the BCD outputs to their high-impedance state.

SPECIFICATIONS

CONTROL-LOGIC INPUTS
Logical "0": 0 to 0.5 V
Logical "1": 2.4 to 5.5 V
Input load: 0.5 TTL unit loads at 5 V

BCD AND CONTROL-LOGIC OUTPUTS
Logical "0": 0 to 0.5 V
Logical "1": 4.0 to 5.5 V
Output drive: 1 TTL unit load at 5 V
Hi-Z state: 25 µA leakage at 2.4 V

POWER
DC voltage: 5 V dc ±5%, 50 mA (nominal)
Source of power: Host DPM

ENVIRONMENTAL
Operating temperature: 0 to 50°C
Storage temperature: -40 to +85°C
Relative humidity: 95% at 40°C(non-condensing)

MECHANICAL
Form factor: Newport DIN 1A upper board
Dimensions: 3.35 x 4.69 in (85 x 119 mm)
Connector: 36-pin, double-row, solder-type

The tri-state,parellel BCD outputs from several digital panel meters may be bushed together for monitoring at central locaion by a programmable controller or remote display.The meter being read is selected by an enable line from a programmable controller or a manual switch. All non-selected meters go into a high-impendance state so as not to affect the BCD bus.