Touchcal TechnologyTouchCAL technology allows easy field ranging for any of the thermocouple or RTD input types. For example, the dip switch configured range for the J type thermocouple is -210 to 760°C. Using a thermocouple simulator as a reference, the model Q488 could be ranged for 0 to 50°C or 0 to 500°C by simply applying the desired minimum and maximum input levels and pushing the range button to store the levels in non-volatile memory. The output is ranged by applying an input signal to achieve an accurate output level and pushing the range button.

Applications
The ActionI/Q model Q488 field configurable thermocouple or RTD input isolator is useful in eliminating ground loops and interfacing temperature sensors to data acquisition and control systems.

Three-way isolation completely eliminates ground loops from any source. Isolation protects expensive SCADA systems from ground faults and allows the noise reduction benefits of grounded thermocouples or sensors to be realized.

The Q488 employs the latest analog to digital signal processing technology and advanced low-power microprocessors. Instant Accuracy cold-junction-compensation (CJC) of thermocouples and lead length compensation for RTDs ensures an extremely accurate and stable signal for virtually any temperature sensor to DC signal conversion.

High density DIN rail mounting offers a very compact solution and saves valuable panel space. Power is delivered to the Q488 via the SnapLocTM terminal block or using the exclusive I/QRail which reduces wiring requirements and the need to daisy- chain power. SnapLoc terminals ensure easy installation and low Mean-Time-To-Repair (MTTR).

Diagnostic LEDs
The Q488 is equipped with front panel LEDs for input power (green-on), input over- and under-range and input open circuit (yellowflash) and switch setting error (red-on). If the input is out of range or open circuit the LEDs provide a clear indication of the error.

Touchcal
The Q488 utilizes Action Instruments’ TouchCAL technology which greatly simplifies set up. Once the unit is configured via DIP switches for input and output type, the push-button is used to precisely set up the minimum and maximum levels.

To set the input level, within the DIP switch configured range, the user simply applies the high input signal (t/c, millivolts or ohms) and pushes the CAL button. The low input signal is then applied and pushing the CAL button again stores the low input signal level.

The high and low input levels are stored in nonvolatile memory and correspond to the high and low output levels. These output levels are precisely adjusted using the input signal reference.

Configuration
A major advantage of the Q488 is its wide ranging capabilities and ease of configuration. The Q488 can be configured via DIP switches for a wide variety of temperature input ranges for RTD, thermocouple, ohm and millivolt sensors.

Each type of input and its respective temperature span can be offset by >90% or adjusted down to <10% of the full scale span.

Unless a specific customer range is specified, the factory presets the Model Q488 as follows:

Regarding other I/O ranges, refer to DIP switch settings (SW2 & SW3) in Table 1 through 9. For quick and easy push button ranging, see the step by step flow chart in Figure 1.

1. With power off, snap off the face plate by lifting the right edge, away from the heat sink. Slide off the heat sink. The two switch banks (SW2 & SW3) should now be accessible.
2. For RTD or Resistance inputs set position 1 and 2 of SW2 for 2, 3 or 4 wire resistance input (see Table 1). For thermocouple inputs these switch positions are not used and can be in any state.
3. Next, the output should be configured for voltage or current using position 3 of SW2 (see Table 2).
4. If the input range desired is the full scale range for the input type (e.g. Pt100W = -200°C to 850°C), then set position 4 of SW2 to ON (or closed) for this default range (see Table 3). If configuration of a sub-range is preferred (e.g. Pt100W, 0 to 500°C), then set position 4 of SW2 to OFF (or open) to enable use of the ranging push button adjustment.
5. If the output range desired is the full scale range for the output type (e.g. 4-20mA or 2- 10V), then set position 5 of SW2 to ON for either of the full scale default output ranges (see Table 4). If configuration of a sub-range is preferred (e.g. 12-20mA or 1-5V), then set position 5 of SW2 to OFF (or open) to enable use of the ranging push button adjustment.
6. Set Burnout detection with position 6 of SW2 (see Table 5). The ON position (up scale) will force the output beyond full scale when the t/c input is open circuit. The OFF position (down scale) will force the output below 0% when the input is open circuit.
7. Set t/c Linearization function with position 7 of SW2 (see Table 6). The ON position will provide an output linear to the temperature input signal. The OFF position will provide an output directly proportional the thermoelectric voltage input (i.e. not linearized to temperature). Note: The unit must be configured with linearization turned ON. Once the configuration is saved, linearization can then be turned OFF.
8. Set Configuration Mode with position 8 of SW2 to ON for DIP switch configuration (see Table 7). The OFF position is for use when configuring via PC with serial interface cable model C681.
9. Set Input Type with position 1 and 2 of SW3 for the specific input type (see Table 8).
10. Set position 3 through 6 of SW3 for the specific RTD, thermocouple, millivolt or resistance input (see Table 9).

Calibration
The Q488 is a microprocessor based circuit with internal references that are factory calibrated to better than 0.000005V. For this reason the Q488 does not need field calibration, but it can be configured (ranged) in the field for virtually any temperature to DC I/O combination.

For best results ranging should be performed in the operating installation, allowing at least 30 minutes for thermal equilibrium of the system. If ranging on a test bench is prefered, then an output load equal to the input impedance of the intended system device(s) connected to the output is recommended, along with a 30 minute warm up period.

1. If the input and the output range needs to be set, then after configuring the unit for the desired I/O, install the module onto a piece of DIN rail or the I/Q Rail mounting combination (see I/Q Rail data sheet for details).
2. According to the selected input type connect the input to a calibrated thermocouple simulator, voltage standard or resistance source and the output to a voltage or current meter. Apply power and allow the system to reach thermal equilibrium (approx. 30 minutes).
3. Adjust the input signal to the desired maximum and observe that the green LED is on. Push the CAL button and hold it down for more than 5 seconds, until the yellow and red LEDs are on.
4. To proceed, push the CAL button momentarily, the yellow and green LEDs should now be on.
5. Apply the maximum input signal level, if not already applied, then push the CAL button to store. The yellow LED should now be on.
6. Apply the minimum input signal level, then push the CAL button to store. The green and red LEDs should now be on.
7. Adjust the input signal up, until the output is precisely at the desired maximum level (e.g. 20.00mA), then push the CAL button to store. The red LED should be on.
8. Adjust the input signal level down, until the output is precisely at the desired minimum level (e.g. 4.00mA), then push the CAL button to store. The yellow, green and red LEDs should now be on.
9. To finish calibration, push the CAL button one final time. The green LED should be on if the input is within the calibrated range.