7. Operation: External User I/O¶
The analog-digital inputs and outputs for the External User I/O port are reconfigurable, allowing the pins to be assigned according to the application and desired parameters. Therefore, the External User I/O pins are grouped according to function, with numerous selectable parameters in the following groupings: Analog Inputs, Analog Outputs, Digital Inputs, and Digital Outputs. Refer to each of these sections for the various parameters that can be assigned to the External User I/O pins.
Note
Not all pins need to be set
Fig. 7.1 External User I/O D-Sub 25-pin Connector and Pin Layout
The following table provides the External User I/O pin layout:
| User I/O Pin | Designation | Description |
|---|---|---|
| 1 | GND ANALOG | Ground (Analog Reference) |
| 2 | +10V REF | 10V Reference Voltage, 20 mA max |
| 14 | +5V | 5V Reference Voltage, 20 mA max |
| 25 | GND | Ground |
| 5 | AI0 | Analog Input |
| 6 | AI1 | Analog Input (High Speed) |
| 17 | AI2 | Analog Input |
| 18 | AI3 | Analog Input |
| 3 | AO0 | Analog Output |
| 4 | AO1 | Analog Output |
| 15 | AO2 | Analog Output |
| 16 | AO3 | Analog Output |
| 11 | DI0 | Digital Input |
| 12 | DI1 | Digital Input |
| 23 | DI2 | Digital Input |
| 24 | DI3 | Digital Input |
| 7 | DO0 | Digital Input |
| 8 | DO1 | Digital Output |
| 9 | DO2 | Digital Output |
| 10 | DO3 | Digital Output |
| 19 | DO4 | Digital Output |
| 20 | DO5 | Digital Output |
| 21 | DO6 | Digital Output |
| 22 | DO7 | Digital Output |
| 13 | NC | No Connection |
7.1. Analog Inputs¶
The WRx Series MagnaLOAD DC electronic load has four analog inputs on its rear External User I/O 25-pin port. The External User I/O pin layout is defined in Operation: External User I/O.
The four analog inputs (Pins 5, 6, 17, 18) can be configured to select different trip or set point values. For the inputs to take effect, Analog Input must be selected in the Set Point Source menu. By factory default, the analog input is disabled. If the source is selected, and one leaves the pin floating, the signal is pulled down resulting in a zero set point.
Standard analog inputs (Pins 5, 17, 18) are used for applications requiring high stability. Inputs are sampled and digitally filtered heavily to remove measurement noise and produce a stable input signals. High-speed analog input (Pin 6) is used for applications requiring fast changes. Here, the input is not filtered and updates every 500 μs.
The following table provides the selection of the available analog input parameters:
| Parameter | Description | Input Reference Voltage Range | Corresponding Output Range | Default Pin |
|---|---|---|---|---|
| Vset | Voltage Set Point | 0-10V | 0-100% of maximum rated voltage | None |
| Iset | Current Set Point | 0-10V | 0-100% of maximum rated current | Pin 5 |
| Pset | Power Set Point | 0-10V | 0-100% of maximum rated power | None |
| OVT | Voltage Trip Point Setting | 0-10V | 10%-110% of maximum rated voltage | None |
| OCT | Current Trip Point Setting | 0-10V | 10%-110% of maximum rated current | None |
| OPT | Power Trip Point Setting | 0-10V | 10%-110% of maximum rated power | None |
A 0-10V input on the Voltage, Current, and Power Set Point input parameters corresponds to a proportional setting of 0-100% of product’s maximum rated voltage, current, and power, respectively. As trip point settings are available up to 110% of the MagnaLOAD electronic load’s maximum ratings, a 10V input on these trip points settings will correspond to 110% of the unit’s maximum rating.
Note
Applying the same voltage reference to a set point input and its corresponding trip point setting is a common way to minimize the number of connections necessary from controlling hardware. With the same voltage reference on the two corresponding inputs, the product will be provided with a set point and then a trip setting 10% above that value. For example, applying the same +5V reference signal for both Vset and OVT on a product rated for 500 Vdc maximum, will correspond to a Voltage Set Point of 250 Vdc and a OVT setting of 275 Vdc.
If an analog input signal is enabled on the External User I/O, a voltage reference must be provided on the selected pin for that parameter. With the input signal enabled, the MagnaLOAD electronic load will no longer reference the digitally stored values for that parameter, meaning no other programming method will be available for that parameter as long as it’s assigned to an analog input. For example, if the user enables Iset on one of the analog input signals, Iset can no longer be programmed from the front panel or computer interface; instead, the user needs to provide a 0-10 V reference on the selected pin.
The analog reference ground is provided on Pin 1 of the External User I/O. As the MagnaLOAD electronic load’s power processing stages can develop electrical noise on the earth ground, this analog reference ground is provided as a clean reference control ground path allowing for accurate low-level voltage programming and measurement. The analog reference ground is tied to the product’s earth ground through resistance, to help filter any noise on the ground.
The set points driven by the analog inputs are visible on the front panel set point menu and can also be queried from the computer interface. Similarly, the trip point settings driven by the analog inputs are visible on the front panel trip point sub-menu and can be queried from the computer interface.
7.2. Analog Outputs¶
The following table provides the selection of the available analog output parameters:
| Parameter | Description | Output Reference Voltage Range | Corresponding Output Range | Default Pin |
|---|---|---|---|---|
| Vin | Measured Input Voltage | 0-10V | 0-100% of maximum voltage | Pin 4 |
| Iin | Measured Input Current | 0-10V | 0-100% of maximum current | Pin 3 |
| Pin | Measured Input Power | 0-10V | 0-100% of maximum power | None |
| Rin | Resistance Set Point | 0-10V | 100%-0 of maximum resistance | None |
The voltage, power, and resistance measurements provided by the analog outputs are measured at the configured sense location. If remote sense is enabled, the measurement will be taken at the sense leads; otherwise, the measurement will be taken at locally at the DC input terminals.
7.3. Digital Inputs¶
The WRx Series MagnaLOAD DC electronic load has four digital input signals on its rear External User I/O. The External User I/O pin layout is defined in Operation: External User I/O.
The four digital inputs are reconfigurable, allowing the user to change the pin assignments. The pin assignment can be modified from the front panel or from the MagnaWEB software.
Each digital input function is activated using +5V logic, but the logic varies among the available functions. This logic used by each function is detailed in the table below.
The digital input impedance is 10 kΩ.
A +5V reference signal is provided on Pin 14. This reference signal may be used in conjunction with external dry contacts to trigger the digital input functions.
Note
For safety, the Stop function will always take precedence over the Start function.
The following table provides the selection of the available digital input parameters:
| Command/Function | Description | Default Pin | Logic |
|---|---|---|---|
| Input Enable | 1-pin alternative to the Start-Stop commands. | Pin 11 | Active When Present |
| Interlock | Normal operation requires a +5V assertion signal. | None | Normally Closed |
| Clear | Removes fault status if the fault is no longer present. | None | Active When Present |
| Lock | Block inputs from front panel keypresses. | None | Active When Present |
7.3.1. Digital Input Logic Definitions¶
- Momentary
- The function is triggered by the momentary rising edge of a +5V signal. The minimum pulse duration to activate a momentary digital input function is 3 ms.
- Normally Closed
- When the function has been assigned to a pin, +5V must be present on the designated pin for normal operation. When the +5V is removed, the function will be triggered.
- Active When Present
- The function is active as long as +5V is present on the designated pin.
7.4. Digital Outputs¶
The WRx Series MagnaLOAD DC electronic load has eight digital output signals on its rear External User I/O. The External User I/O pin layout is defined in Operation: External User I/O.
The eight digital outputs are reconfigurable, allowing the user to change their pin assignments. The pin assignment can be modified from the front panel.
The digital outputs are used to monitor the MagnaLOAD electronic load’s internal states. A pin will output +5V when a state is active and 0V when a state is inactive. The maximum output current per pin is 20mA.
Caution
Trying to drawing more than 32 mA from a digital output will damage the MagnaLOAD electronic load’s controller.
The following table provides the selection of the available digital output parameters:
| State | Description | Default Assignment |
|---|---|---|
| Enabled | The input is engaged and the MagnaLOAD electronic load is processing power | Pin 7 |
| Standby/Fault | The MagnaLOAD electronic load is either in a standby or faulted state | None |
| Standby | The MagnaLOAD electronic load is in standby | Pin 8 |
| Fault | The MagnaLOAD electronic load is in a faulted state | Pin 9 |
| CV Regulation | The MagnaLOAD electronic load is regulating voltage | None |
| CC Regulation | The MagnaLOAD electronic load is regulating current | None |
| CP Regulation | The MagnaLOAD electronic load is regulating power | None |
| CR Regulation | The MagnaLOAD electronic load is regulating resistance | None |
| Lock | The lock function is active and the MagnaLOAD electronic load is locked | None |