Metering Inputs (DV-200)

Metering inputs (xAyy)

This section explains how to configure the Metering Inputs. Each metering input is programmed individually according to its use and function.

Note: Previously, recalibration of the metering inputs was required if the RAM battery was removed, if the processor board was changed, if an I/O board was repaired, changed, or moved to another position in the Davicom unit, and if trueRMS converter chips were added, or jumper-activated. Refer to Chapter 19 of the Reference Manual for updated information regarding calibration procedures.

To configure metering inputs, click the Unit Configuration icon () then on the Inputs tab and select Metering Inputs.

Metering Inputs configuration dialog box

Example from image above: Metering input 1A04 is connected to a temperature sensor in the rack room. When temperature is below +15 ºC, physical relay 1R05 automatically turns on a heater. When temperature is below -10 ºC or above +35 ºC, a major alarm is sent to recipients of the Major 1 Alarm-Call List.

The upper portion of the Metering Inputs Configuration dialog box allows you to set the following parameters:

Input Number: Select from the dropdown list the number of the specific metering input you wish to configure. Metering inputs are all identified by the A letter, followed by one or two digits (up to 32 depending on your Davicom model).

Note: Input Numbers will begin by a digit (1 to 4) to identify a specific Davicom unit when several DV-208/216 units are networked together (SuperMAC), or when MEXM /Modbus slave units are connected. Otherwise it must begin with the digit 1.

Enable: Check this box to enable the input and its automatic actions. When disabled, no reading is taken from the input. You can also enable/disable metering inputs by using the Enable and Disable buttons on the DavLink Command Bar (refer to Section 16.1.4 on page 279 of the Reference Manual).

Qualifier: A qualifying condition, which can be another input, output, timer, flag, etc., can be used to control the actions of the metering input. In State mode (the default setting), the condition must be satisfied (true) in order for the Davicom to execute programmed actions when the metering input is outside prescribed limits. In Data mode, the metering input will only be free to update its value when the qualifying condition is true; otherwise it remains “frozen” at its current value. Any condition can be inverted by adding the exclamation sign “!” before the conditioning input ID (!1S01 for example).

Default Description: Long Unicode description for each metering input. (Maximum 30 alphanumerical Unicode characters). Refer to this article for more details.

Alternate Description: Short ASCII description for each metering input. (Maximum 18 alphanumerical ASCII characters).

Voltage Range: Select from the dropdown list the voltage range (in volts) used by the sensor connected to the metering input. Available ranges are 2.5, 10 and 20, for the following peak-to-peak voltages: –2.5 V to +2.5 V, –10 V to +10 V, and –20 V to +20 V. RAW range can be selected for Modbus modules.

Notes: Jumper settings inside the Davicom unit must correspond to the selected range (refer to Section 6.1 on page 159 of the Reference Manual). For 4-20 mA sensors, select 2.5 for Voltage Range (refer to Figure 110 on page 163 of the Reference Manual). For more information on unipolar and bipolar connections, refer to Section 6.1.1 on page 159 of the Reference Manual. New DV-Mini units (blue & grey front panel) have the same ranges as the Davicom DV-208/216 units but older Davicom MiniMAC units (black front panel) have unipolar 0–2.5 V, 0-10V, and 0-40 V ranges. DV-Micro units have fixed 0-5 V inputs.

Measurement Unit: Select from the dropdown list the measurement display unit that you want to assign to the selected input. Over 25 pre-defined display units are provided for your convenience. You can also enter your own 3-character unit if it is not available in the dropdown list. Note that these units are just for display purposes, and only the SWR unit actually does a calculation based on the meter voltage readings.

Note: SWR is the 3-character abbreviation for VSWR. When SWR is selected for the input measurement unit, the Davicom will use this input, combined WITH the preceding input, to automatically calculate the VSWR from the forward and reflected power measurements. This input is thus used to measure reflected power, and the preceding input measures forward power).

Normal Value: Enter the normal operating value. This value corresponds to the reference level that is considered normal, and is used only to set the display scale for the Metering Gauges (refer to Section 11.3.2.6 on page 223 of the Reference Manual).

Sensor Coefficients: Default values are A=0, B=1, C=0 and D=0. This assumes that there is a direct 1 to 1 relation between the measured voltage or current and the sensor’s output. For other transfer functions, you can use the Davicom’s built-in sensor curve fitting feature by entering the A, B and C coefficients of the Ax2 + Bx +C equation. The Davicom sensor curve fitting utility can help you calculate these A, B and C coefficients (refer to Section 2 Analog sensor curve fitting function). Once the A, B and C parameters are determined, you can set D=10 for voltage readings proportional to power (in dB), or D=20 for voltage readings proportional to the square root of power (in dB). If using the optional Davicom True-RMS Converter chips, set A=0, B=1.29, C=0 and D=20 for readings in dBu, and keep the default values for readings in dBV.

The lower portion of the Metering Inputs screen is divided into three tabs. To configure a Vocal Description, refer to this article. For Modbus information, please refer to the Davicom Expansion Module (MEXM) manual and other Support documentation on the Davicom website. To configure automatic Actions, set the following parameters:

Level1 and Level2 Considering normal operation corresponds to the green zone on Metering Gauges (refer to Section 11.3.2.6 on page 223 of the Reference Manual), Level1 settings would typically correspond to the yellow warning zone generating for example a minor alarm, while the Level2 settings would typically correspond to the red critical zone generating a major alarm. Each level has the same configurable fields. You can use only Level1, leaving Level 2 fields blank, or use both levels by providing different values for each level. Each level can act on different relays.

Tip: By setting the Level1 Low Limit to ✻ (star) and the Level1 High Limit to the maximum allowed indoor temperature, and the Level2 Low Limit to the minimum allowed indoor temperature and the Level2 High Limit to ✻ (star), you can have the Davicom energize the air conditioning relay when temperature goes above the Level1 High Limit, and the heater relay when temperature goes below the Level2 Low Limit.

Action Type: For each Level, select from the dropdown list the action (MIN, MAJ, CMD or QLF) that will automatically be performed by the Davicom unit when a qualifying condition (if applicable) confirms that the value of the metering input has reached its Low or High Limit. Refer to this article for more details.

Alarm-Call List: If you selected MIN or MAJ for Action Type, you need to select a specific Alarm-Call List from the dropdown list (1 to 8). Refer to this article for more details on alarm-call lists.

Low Limit: For each Level, this is the measured value below which the programmed automatic action will be performed by the Davicom unit. Maximum 6 digits without decimals, maximum 4 digits after the point.

Hysteresis (Low): Once the Low Limit has been reached and the appropriate automatic Action has been taken, small oscillations of the input signal might occur around the Low Limit. To prevent false Return to Normal messages and false automatic Actions to be performed repetitively, you can set a Hysteresis value for the Low Limit. This way, Return to Normal condition will only happen once the measured value increases above the Low limit plus Hysteresis Low. Maximum 6 digits without decimals, maximum 4 digits after the point. See image below.

High Limit: For each Level, this is the measured value above which the programmed automatic action will be performed by the Davicom unit. Maximum 6 digits without decimals, maximum 4 digits after the point.

Hysteresis (High): Once the High Limit has been reached and the appropriate automatic Action has been taken, small oscillations of the input signal might occur around the High Limit. To prevent false Return to Normal messages and false automatic Actions to be performed repetitively, you can set a Hysteresis value for the High Limit of each Level. This way, Return to Normal condition will only occur when the measured value decreases below the High limit minus Hysteresis High. Maximum 6 digits without decimals, maximum 4 digits after the point.

For example, consider a metering input with the following Level1 settings: Low Limit of 45, Hysteresis Low of 15, High Limit of 200 and Hysteresis High of 30.

Example of Level1 Limits and Hysteresis

The light grey automatic action zone representing the metering input at its active level begins once the High Limit (200) has been exceeded, and remains in that state for as long as the value of the input remains above the High Limit minus Hysteresis High (200-30=170). The dark grey automatic action zone representing again the metering input at its active level begins once the Low Limit (45) has been reached, and remains in that state for as long as the value of the input remains below the Low Limit plus Hysteresis Low (45+15=60).

Controlled Relays: For each Level, the Davicom can act automatically on up to 6 different relays (physical or virtual) when the metering input has reached the Low or High Limit (subject to a qualifier). Use the xRyy identifier for physical relays and xOyyy for virtual relays. By default, relays will react in the Follow operating mode if you do not add any letter to the relay identifier. For the Latch mode, you must add the letter L to the relay identifier. For the Davicom to pulse a relay, you must add the letter P to its identifier. For the Davicom to release a relay, you must add the letter R to its identifier (1R04R for example).

Note: You must make sure each relay is configured for the operating mode you wish to use. You cannot Latch a relay that is configured as Pulse Only for example. Refer to this article for more details on relay configuration.

Automatic Limit Change Qualifier: An optional qualifying condition can be set to automatically apply a common multiplication factor to all Level1 and Level2 Limits. For example, when a back-up transmitter of lower power than the main transmitter (5KW vs 10KW) takes over operation, the appropriate qualifier applies a multiplier (0.5) to all limits, ensuring proper limits are applied for monitoring of the back-up transmitter.

Multiplier: If you entered an Automatic Limit Change Qualifier, you must enter the appropriate Multiplier that will apply to all Level1 and Level2 Limits. Decimal values are allowed in order to obtain a divider. Maximum 5 digits, maximum 3 decimal places.

Metering Window Low: Optional field that allows you to manually set the lowest value on the scale of the Metering gauge associated with the selected metering input. If you leave this field blank, DavLink will automatically display the gauge with an adequate scale. Refer to Section 11.3.2.6 on page 223 of the Reference Manual for more information on gauges.

Metering Window High: Same as previous, but for the highest value on the scale of the Metering gauge.

Alarm Signalling On: If you selected the MIN or MAJ Action Type for one or both levels, you need to check this box for the Davicom to initiate the appropriate Alarm-Call Sequence (ACS) when a qualifying condition (if applicable) confirms that the value of the selected metering input has reached the Low or High Limit. If you do not check this box, no ACS will be initiated, but the Davicom will still log alarms (MAJ and MIN) and commands (CMD), and act on relays. Refer to this article for more information on the ACS.

Return to Normal Signalling On: If you selected the MIN or MAJ Action Type for one or both levels, you need to check this box if you want the Davicom to initiate the appropriate ACS to report a Return to Normal when the value of the selected metering input increases above the Low limit plus Hysteresis Low, or decreases below the High limit minus Hysteresis High. If you do not check this box, no ACS will be initiated, but the Davicom will still log the Return to Normal (for MAJ, MIN and CMD) and act on relays.

Delay Before Action: To avoid untimely automatic Actions caused by short-duration false alarms, a delay can be programmed before the Davicom responds to a confirmed out-of-limit condition. This sets the minimum duration that an out-of-limit condition must be in effect before the Davicom considers that it is valid and executes the programmed automatic Actions. Default setting is 0 (no delay). You can select a value between 0 and 9999 seconds using the arrows or by typing-in the number.

Delay Before Return to Normal: To avoid untimely automatic actions caused by short-duration Return to Normal conditions, a delay can be programmed before the Davicom responds to the Return to Normal condition. This sets the minimum duration that the Return to Normal condition must be in effect before the Davicom considers it to be a valid condition, and thus execute the programmed Return to Normal actions. Default setting is 0 (no delay). You can select a value between 0 and 9999 seconds using the arrows or by typing-in the number.

Custom Log: Davicom units can provide one custom log in addition to the extensive system log. This allows Davicom users to focus-in on desired information. Check this box if you want to record events related to the selected metering input in the custom log. This setting also enables periodic data logging (refer to Section 4.7.3.1 on page 138 of the Reference Manual for more details).

Analog sensor curve fitting function

The Davicom allows linearization of sensors using equations that can be modified with various coefficients to compensate for non-linear sensor behaviour. The general conversion formula is y= Ax2 + Bx + C which applies a least squares curve fitting to a series of sensor readings. This formula can be used to linearize and adjust for nearly any sensor type available. Sensors are assumed to have a linear unity gain, no offset behaviour (y=x with A=0, B=1 and C=0) in the default Metering Input configuration (refer to Section 1 Metering inputs (xAyy)). When you change any of these coefficients, the scale of the DavLink Metering gauges automatically adapts to the appropriate range for the sensors (refer to Section 11.3.2.6 on page 223 of the Reference Manual).

Note: Linearization is not the same as calibrating the Davicom metering inputs using special calibration connectors. Calibration is no longer required (see Chapter 19, page 293 of the Reference Manual).

The B coefficient represents a gain (or attenuation) factor. Any B coefficient greater than 1 expands the measurement scale displayed on Metering gauges. A non-zero value for the A coefficient adds more amplification to the sensitivity and, combined with a higher scale setting, may cause greater fluctuation in meter readings. The C coefficient is an offset factor. The D coefficient is not used for curve fitting, but to convert power readings with measurement units other than Watts (dBm, dBu, etc.).

Sensor manufacturers sometimes give linearization parameters for their sensors. If sensor parameters are not provided, the DavLink software has a built-in Function Generator utility. Right clicking on one of the A, B, C or D Sensor Coefficients edit boxes will bring you to the Function Generator utility as shown below. The generated A, B, C and D Sensor Coefficients will be applied on OK and aborted on Cancel.

Function Generator

Add new point: To add a new point to the graph, double click at the position the new point should be located. Sensor coefficients will be updated automatically.

Remove a point: To remove a point from the graph, double click on the point to remove. Sensor coefficients will be updated automatically.

Move a point: To move a point on the graph, left click on the point to move and drag it to the new position. Sensor coefficients will be updated automatically.

Note: When moving a point, the Current Cursor Position indicator at the bottom left corner of the dialog box gives the exact point position on the graph.

Zoom X scale: To horizontally zoom the graph, use the [+] and [-] buttons next to the X: in the Zoom section.

Zoom Y scale: To vertically zoom the graph, use the [+] and [-] buttons next to the Y: in the Zoom section.

Reset View: The Reset View button clears all data and the graphic display.

View Function Table button: The View Function Table button shows the results of the least mean squares calculations.

View Point Table button: Points can be managed by using the Point Table dialog box. To access the Point Table, click on the View Point Table button as shown on the Function Generator screen. Modifications will be applied on OK or aborted on Cancel.

Point Table

Add new point: To add a new point in the list, double click on an empty line and edit values in the bottom edit boxes.

Remove a point: To remove a point from the list, double click on the line to remove.

Change a point value: To change a point value, left click on the line to change and edit values in the bottom edit boxes.

A Davicom sensor curve fitting utility is included in the Davicom installation DVD. It is part of the Davicom Firmware & Utilities package which is installed by default in the C:\Program Files\Davicom\Davicom\Utilities directory (refer to this article). The utility is an Excel spreadsheet file (DavSensorCurveFitting.xls). After the values for the A, B and C coefficients have been determined, go back to DavLink and enter them in the Sensor Coefficients fields when configuring the Metering Input to which the sensor is connected.

Note: All metering input signals go through buffering, conditioning and amplification stages before A/D conversion by a 12-bit converter. Resistor values used in these stages are 1% precision, meaning that the best possible accuracy for the Davicom metering display is 1%. Note that the number of significant digits depends on the selected scale. The 12-bit converter gives a theoretical dynamic range of 72 dB, which implies a resolution of about 10 mV on the 20 V scale, and 1.2 mV on the 2.5 V scale.

Metering mathematical functions (xFyy)

This section explains how to configure the Metering Math Functions (MMF). Each metering math function is programmed individually according to its use and function.

To configure metering math functions, click the Unit Configuration icon () then on the Inputs tab and select Metering Math Functions.

Example from image above: Metering Math function 1F01 calculates the main transmitter power output by multiplying the transmitter voltage (around 72 Vdc measured by 1A07) by the transmitter current (around 35 A measured by 1A08). To translate these front panel meter values to the real rated power output of the transmitter, an efficiency factor of 0.85 is applied to account for output circuit and filter losses.

Metering Math Functions are configured exactly the same way as for Metering Inputs (refer to Section 1 Metering inputs (xAyy)). The only differences are: an identifier using a different letter, the maximum number of functions, the Voltage Range dropdown list is replaced by an Operator dropdown list, and the four Sensor Coefficients are replaced by five Operands. These differing fields are described below:

Func Number: Select from the dropdown list the number of the specific Metering Math Function you wish to configure. Metering Math Functions are all identified by the letter F, followed by one or two digits (up to 16).

Note: Func Number will begin by a digit (1 to 4) to identify a specific Davicom unit when several DV-208/216 units are networked together (SuperMAC). Otherwise, it must begin with the digit 1.

Operator: The mathematical operator (+, – , x , /, LOG 10) applied to all the Operands in order to produce the resulting value.

Operands: Up to 5 Operands can be entered as inputs for the selected Metering Math Function. Operands must either be constants, Metering Inputs, the DVLD distance value 1LD1, or another 1Fxx function. Metering Inputs cannot be inverted (i.e. !xAyy is not valid). Constants can be a maximum of 5 digits before or after the decimal point, or a combination, like 12.345, 123.45 etc..

Note: If you have more than 5 Operands, you can cascade several Metering Math Functions. When less than 5 Operands are used, empty or disabled Operands are considered to be 1 for ✻ and / Operators, and to be 0 for + and – Operators.

LOGARITHM Operator

The Metering Math functions also have a Base 10 Logarithm operator (log10X) that allows you to convert voltage or power readings to dB, dBm, dBV or dBW.

Metering Math Functions configuration (LOGARITHM Operator)

To use this operator, you must go to the Metering Math Functions window (see image above) and select the LOG 10 operator. The result is calculated as follows: Result = (1st field) x log10(2nd field) In the example shown in the image above, Result = 20 log10(1A02) The operands allowed are:

  • Constants (ex: 10, 0.5, 20)
  • Metering Inputs (ex: 1A02, 3A16, 2A01)
  • Other Metering Math functions (1F02, 2F04, 4F06)
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