Using Existing AquaCalc 5000s
having the Basic (G) firmware,
with the new Standard Rating Table No. 2

Updated June 30, 1999

The following is an updated version of the instructions contained in Using Current Meters with the AquaCalc chapter under the heading Using Non-Standard Current Meters of the operating instructions for the AquaCalc 5000 using the Basic (G) firmware.

These instructions have been updated to reflect problems with two segment meter equations and changes in the Standard Rating Tables for the Price type AA and pygmy meters as discussed in the technical Memorandum No. 99.05, released by the The Office of Surface Water, United States Geological Service on June 2 , 1999. Due to the changes in the Rating Tables and associated equations, the default ratings for the Price type AA and pygmy current meters are no longer correct. Until your AquaCalc is updated, you must use the Non-Standard meter function to enter the new Standard Rating Table No. 2 equations into the AquaCalc and use these while measuring.

In addition the current version of the firmware cannot accommodate the four decimal place constants of the new equations. These must be rounded to three decimal places, resulting in an average overestimation of the velocity in each vertical of approximately 0.02 percent.. A firmware update will soon be available to expand the decimal places and update the default values for the Price type AA and pygmy meter rating equations.

These instructions will not work with the Advanced (H) firmware. Please see the Advanced Instructions.

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Important Note:  Your existing manual is incorrect! All existing AquaCalc 5000 Basic (G) series units cannot be used with user-defined non-standard meters having a two segment meter rating curve unless the intercept value of the two segments is 2.2. Please see the explanation of rating curve line segments below. The constant value referred to below as the intersect (C5) is fixed in existing Basic firmware with a value of 2.2 and cannot be changed by the user. This two segment line was intended to be used with an ice meter only, something not mentioned in the manual. Using other two segment meter rating curves may lead to incorrect measurements! We will be including a fifth constant (C5) in the updated version of the firmware. This new firmware version will also correct for the new Standard Rating Table equations and the four decimal place entry requirements. This will allow you to use any two segment rating equation. Please contact Customer Support for information on upgrading your firmware.

Contents
Overview
Meter Rating Equations
Entering Single-Segment Rating Equations
Entering Two-Segment Rating Equations
AquaCalc Meter Constants (C1-C4)
Step-by-Step Instructions
Rating Table Equation Values
Setting the Meter ID

Overview

In addition to the built in current meter rating curves for the default Price AA and Pygmy meters (Note: Existing firmware has the rating curves for the Standard Rating Table / Equation No. 1), the AquaCalc 5000, using the Basic (G) software, can store the rating curves for a user-defined / “nonstandard” current meter in each transect. The hydrographer must re-enter the meter constants in each of the transects that he/she wishes to use a user-defined or non-standard meter.

To use a user-defined / nonstandard current meter, the user needs to know the “rating curve” or the equation that defines the relationship between the number of revolutions per second (R) that the cups spin, and the measured velocity.

If you are using a metric meter please see Non-Standard Metric heading of the Using Your AquaCalc chapter.

Meter Rating Equations

As used by the USGS, meter rating curves are either a single or a pair of equations that define the relationship between the number of revolutions per second of the current meter cups and measured water velocity. The equation for a single or for each segment of a pair of equations equation takes the form:

Y = m*X + b

or

Velocity=(m*X*( Revolutions/Second)) + b

where m is the slope of the line, and b is the intercept. Some current meters, such as a Type AA, use two equations: one of which is used for lower velocities, the other for higher. A crossover velocity is also specified. An example of a Type AA Rating Table with the equations is shown below. 

Entering Single Segment Rating Equations
(i.e.: new Standard Rating Table No. 2 - 6/99)

In the new Standard Rating Table No. 2, the equation for a Price type AA meter is:

EQUATION: V = 2.2048 R + .0178

In this equation, R is the revolutions / second, V is the velocity. The above equation is interpreted as a single segment line.

Velocity= 2.2048 x rev/sec + .0178

User-defined / non-standard current meter rating curves are stored in the AquaCalc as a series of five “constants” that represent the two equations or intersecting lines of a meter rating curve. Only two values are used in a single segment line, but these are repeated and a dummy fifth constant is used.

Constants C1 and C2 correspond to m1, and b1 for the single segment equation.

Due to the way the AquaCalc 5000 handles single segment equations, you must repeat the same values in constants C3 and C4, and place a value of 1.000 in constant C5.

In addition, the current version of firmware can only handle three places after the decimal so all constants must be rounded to the third decimal place.

So for the sample Price Type AA Standard Rating Table No. 2 (6/99) equation used above:

EQUATIONS: V=2.2048R + .0178

The constants to be entered are:

• C1 = 2.205
• C2 = 0.018
• C3 = 2.205
• C4 = 0.018

Please see the Step-by-Step: Setting Current Meter Ratings below for instructions on entering these constants in a user-defined meter. Values for the equations for pygmy meters are also listed below.

Entering Two-Segment Rating Equations for Ice meters having an intercept value of 2.2

The AquaCalc 5000 using the Basic (G) firmware can be used with ice meters having a two segment equation an intercept value of 2.2. It may not be used with two segment equation having an intercept value other than 2.2. (See the note above.) The USGS Standard Rating Equation No. 1 for a Type AA current meter (which does have an intercept of 2.2) is shown on the Standard Rating Table No. 1 as:

EQUATIONS: V=2.18R + .20(2.200) 2.170R + .030

In this equation, R is the revolutions / second, V is the velocity. The above equation is interpreted as two line segments, with the velocity at which they intersect in parenthesis:

Line 1: Velocity1= 2.180 x rev/sec + .020

for velocities greater than 2.200 the equation is

Line 2: Velocity2 = 2.170 x rev/sec +.030

These equations can be represented as two intersecting lines on a graph as in the following figure

.

AquaCalc Meter Constants

Nonstandard current meter rating curves are stored in the AquaCalc 5000 using the Basic (G) firmware as a series of four “constants” that represent the two equations or intersecting lines of a meter rating curve. A “hidden” fifth constant (C5) is fixed with the value of 2.2. This is to be used with ice meters only.

Constants C1 and C2 correspond to m1, and b1 for the first equation respectively and C3 and C4 to m2, and  b2 for the second equation. The constant C5 is the velocity value at the intersection of the two straight lines (currently fixed at 2.2)

If you are entering a single line segment (as in the new Standard Rating Table /Equation No. 2) Enter the same constants for C3 and C4 as you entered for C1 and C2 (C3=C1 and C3=C2).

So for the sample Type AA equation used above:

EQUATIONS: V=2.18R + .020(2.200) 2.170R + .030

The constants to be entered are:

• C1 = 2.18
• C2 = .020
• C3 = 2.170
• C4 = .030

Step-by-Step: Setting Current Meter Ratings

Nonstandard meter settings are setup in the Transect Information Settings menu.

Important: You must perform these steps in every transect you wish to use a user-defined or non-standard meter (including the new Standard Rating No. 2 equation.) Meter constants are not shared between transects.

- Go to the Transect that you wish to measure in while using a user-defined or non-standard meter (including the new Standard Rating No. 2 equation)

- Press the Setup (0) key to access the Main Menu.

- Press the 1 (2 = TrInfo) key to enter the Transect Information Setup. 

- Press Enter until the following screen appears (The bottom line of this screen will list your currently chosen meter type):

Press the +/- key to cycle through the different meter types until you reach the Non-Standard selection:

- Press the Enter key to view the first meter constant.

- Pressing the +/- key will allow you to enter the value for the constant.

Existing AquaCalc firmware can only handle three places after the decimal, you must round off to three decimal places. Once you have entered the value, press Enter. 

The AquaCalc will prompt you for each of the remaining constants C2 through C4 (C5 is fixed at a value of 2.2). Enter them as you entered Constant 1 (C1) above. 

If you are entering a current meter rating that has only one segment (such as the new Standard Meter Rating Table No. 2 equations), repeat the values for C1 and C2 in C3 and C4 (so that C3=C1 and C4=C2). See the sections above for a description of single segment meter constants.

After entering all five “constants”, you will be presented with the Set Measurement Time Screen. Enter the measurement time or press the Setup key (0) to return to the Main Menu.

Rating Table Equation Values for the Price AA and Pygmy meters

The following table shows the values to be entered for Price type AA and pygmy meters and for the new Standard Rating No. 2 equations and the old Standard Rating No. 1.

Note that you must round the new Standard No. 2 values to three decimal places to accommodate the limitations of the current version of AquaCalc 5000 firmware. An update of the firmware is necessary to allow for four decimal place entries. This results in an error of approximately 0.02 percent overestimation for the velocity values. Please see our Customer Support page discussing the New Standards for more information.

Setting the Meter Identifier - METER ID#

You may also set a meter identifier for he meter you use in Meter Identifier screen. This screen appears before the Change Meter Type screen described above and allows you to record the Serial Number or some other identifying number of the current meter used to measure the stream. Up to six digits including a period and a dash can be entered. 

Press the +/- key and enter your METER ID#. Press ENTER to complete the entry.