South Dakota State University
South Dakota Climate and Weather

HOW TO: Setup Vaisala All Weather Precipitation Gauge VRG101 (VRG 101)
with CR10X or CR1000 Campbell Scientific Datalogger

Created: Chirag Shukla
Status: Original author
Date: 10/22/2007
Audience: General/Novice

Revision History: 0.1 (Draft 1)
Changes: Added information that RS-485 brown conductor does not need to be connected to 12V on datalogger. Added informational notes in various locations
Keywords: Vaisala all weather rain gauge VRG101, VRG 101, VRG-101.

Revision History: 0.0 (Initial Draft)
Purpose: VRG101 is a simple-to-use and fine all weather rain gauge manufactured by Vaisala. This all weather precipitation gauge uses AC power for rim heating and operation. This gauge can also output data similar to a tipping bucket rain gauge. Campbell Scientific Inc's (CSI) dataloggers like CR10X and CR1000 can be configured to read output from VRG101. This document highlights key points for novice users to begin using CSI's dataloggers to record data from VRG101
Usage: This "How To" is free to use and distribute with proper citation/credits and without altering this original document. If alterations need to be made, please make the updated version freely and publicly available. Add your name, date of revision, and revision history/number on the top of the original author's header before distributing the updated document. Also make available citiation of orginal document so that new users can review the updates made to this document. Any documentation derived from this document should be made available to general public at no cost to them (free)
Note: Use instructions at your own risk. The author will not be liable for any losses or damages resulting from this documentation

Instruments and materials:

  1. VRG101 [ Purchased from Vaisala ]
  2. AC Power Source, in our case WHP25 [ Purchased from Vaisala ]
  3. CR10X or CR1000, in our case CR1000 [ Purchased from Campbell Scientific ]
  4. Cable with M-12 connector on one end and loose conductors on the other [ specs | picture ] (See note)
  5. Maintenance cable [ Purchased from Vaisala ]
  6. Reference weight / Field check kit [ Purchased from Vaisala ]
  7. Laptop/Desktop with RS-232 serial port
  8. Available AC power
  9. 3-prong desktop computer's CPU power cable chopped off at 3-prong female end

Cable with M-12 connector on one end and loose connectors on the other M-12 connection side view M-12 connection top view

Figure i: Cable with M-12 connector on one end and loose connectors on the other

Cable with M-12 connector on one end and loose connectors on the other, loose connectors stripped

Figure ii: Cable with M-12 connector on one end and loose connectors on the other, loose connectors stripped

Maintenance RS-232 cable

Figure iii: Maintenance RS-232 cable

RS-232 female end RS232 side view M-12 end M-12 end

Figure iv: Maintenance cable (XRO141) with RS-232 end (top and side view) and M-12 end


  1. Assumption is made that user is using Windows XP Professional with Hyperterminal installed. You may use mgetty, minicom, screen, gtkterm, cu etc on Linux. Mac users may use ZTerm to configure VRG101 using serial communication
  2. Cable with M-12 female connector one end and loose/free conductors on the other end can be obtained from Phoenix Contact or one of their distributors. We work with Minneapolis based Stark Electronics:

Stark Electronics
Direct: 612-372-3145
Toll free 888-372-3145
Ask for part number 1683374
Approximate cost is $20 + taxes + shipping. Allow 7 days of lead time.

Preliminary reading:

  1. VRG101 brochure and manual
  2. WHP25 manual
  3. CR10X or CR1000 manual

Please read through VRG101 and WHP25 manual at least once. It is assumed that the reader is experienced in setting up and programming CR10X or CR1000 (or related) Campbell Scientific's dataloggers

WHP25 wiring:

  1. AC power terminated at a extension/power strip with multiple 3-pronged outlets was available for use
  2. Cut the 3-prong female end of a desktop computer power cable and strip the conductors
    Desktop computer power cord cut at female end
    Figure 1: Illustration of a black desktop computer power cord/cable in its original state. White power cable has been cut at the female end and conductors are stripped. Click for higher resolution image.

    Closeup of desktop computer power cable used for VRG101
    Figure 2: Closeup illustration of a black desktop computer power cord/cable in its original state. White power cable has been cut at the female end and conductors are stripped. Click for higher resolution image.
  3. Open WHP25 case. Using a flat end screw driver, open the plastic shield above jumpers (WHP25 manual, figure 3 on page 11)
    WHP25 X1 terminal
    Figure 3: Open the screw to remove plastic shield. Notice the orange colored spring loaded terminals on the top where Line and Neutral AC wires will go. Press the orange springs with a small flat head screw driver to insert conductors. AC ground conductor will travel through the crimper and should be attached tightly to the screw.
  4. Set the jumper to 115 V. Re-seat the plastic shield above the jumpers
    WHP25 115V jumper settings
    Figure 4: Shows jumper settings for 115 VAC
  5. Connect green conductor from desktop computer cable to WHP25's AC ground (WHP25 manual, figure 5, page 12)
    WHP25 and AC wiring
    Figure 4: AC ground, line and neutral lines attached to WHP25
  6. Connect white (neutral) and black (line) conductors to WHP25's X1's spring loaded terminals. Use a flat head screw driver to push down on the springs of the terminal.
  7. Get a 4-conductor cable or two double-conductor cables with free ends on both sides. Strip one end of each conductor
  8. Connect 1st conductor to X4 terminal 4 (WHP35 manual, figure 5 on page 12)
    WHP25 X1 and X4 terminals
    Figure 5: WHP25 X1 and X4 terminals wired
  9. Connect 2nd conductor to X4 terminal 5
    Closeup of WHP25's X4 terminal
    Figure 6: Closeup of WHP25's X4 terminal
  10. Connect 3rd conductor to X4 terminal 6
    WHP25's X4 terminal wired
    Figure 7: WHP25's X4 terminal wired
  11. Connect 4th conductor to X4 terminal 7

Ground :: Ground
Line :: X1 right spring loaded terminal
Neutral :: X1 left spring loaded terminal

VRG101 wiring:

  1. Connect loose end of 1st conductor running from WHP25's X4 terminal 4 to VRG101's VB terminal
    Conductors from WHP25's terminal connected to XRM101
    Figure 8: Conductors from WHP25's terminal connected to XRM101. VRG101's XRM101 terminal wired, RS-485 connected to CR1000 (CR1000 not in picture), RS-232 connected to computer (computer not in picture). Piece of weight sits on the pan. Reference weight (aka field kit) sits under the pan
  2. Connect loose end of 2nd conductor running from WHP25's X4 terminal 5 to VRG101's Heat A in terminal
    Closeup of XRM101's terminal strip
    Figure 9: Closeup of XRM101's terminal strip
  3. Connect loose end of 3rd conductor running from WHP25's X4 terminal 6 to VRG101's Heat B in terminal
    WHP25 is connected to XRM101
    Figure 10: WHP25 is connected to XRM101. Notice Heat A and B out terminals empty.
  4. Connect loose end of 4th conductor running from WHP25's X4 terminal 7 to VRG101's GND terminal
  5. Connect rim heater's one conductor to VRG101's Heat A out and the other to Heat B out (rim heater has 2 conductors)
    VRG101's rim heating conductors
    Figure 11: VRG101's rim heating conductors should connect to Heat A and B out terminals on XRM101
  6. Connect maintenance cable's M-12 connector (5-pin female end) to VRG's RS-232 and 9-pin female end to the serial port of the computer
  7. Connect M-12 female ended cable with loose ends (part 1683374) to RS-485 port of VRG101
  8. Strip the loose conductors. Attach blue to CR1000's ground (besides 12v), brown to 12v, white to C2, black to signal ground (besides EX2)
    CR1000 wiring
    Figure 12: CR1000 wiring. XRM101's RS485 is connected with M-12 ended cable. Other end of the cable is stripped. Blue wire is not visible in the picture. Green/Yellow wire is not connected anywhere

Rim Heater :: VRG101
one conductor :: Heat A out
other :: Heat B out

WHP25's X4 terminal :: VRG101
Terminal 4 :: VB
Terminal 5 :: Heat A in
Terminal 6 :: Heat B in
Terminal 7 :: GND

VRG101 RS-485 :: CR1000
blue :: G
brown :: 12V does not connect anywhere (make sure this conductor is isolated so that it does not touch anything)
white :: C2 (use port P1, P2, C6, C7 or C8 on CR10X)
black :: signal ground (besides EX2)
green/yellow :: does not connect anywhere

(See: Informational Note)

Power up the instruments:

  1. Power up the computer, open Hyperterminal (Start -- Programs -- Accessories -- Communications -- Hyperterminal)
  2. Enter a name when Hyperterminal prompts (e.g. test)
  3. In the Connect To window's Connect using drop down box, select your COM port (serial port)
  4. In COM properties window, choose Bits per second = 9600, Data bits = 8, Parity = None, Stop bits = 1, Flow control = Hardware (or none)
  5. Hyperterminal will display a blank white window
  6. Plug in the 3-prong male end of a desktop computer power cable to the AC power/extension strip
  7. VRG101 will beep 3-4 times once powered
  8. Hyperterminal will receive a "VAISALA VRG101: V2.02 2007-01-29" message from VRG101. This indicates VRG is communicating using serial port

Configure VRG101:

  1. Jump to command mode of VRG101 by typing "OPEN 1" without quotes in Hyperterminal followed by hitting Enter
  2. VRG will prompt for more information using > prompt
  3. > CONF [Enter] will display current settings. Make sure item 2 TIP MM is set to 0.1
  4. If Tip MM is not set to 0.1, type > CONF 2 0.1 [Enter]. Note that there is a space between 2 and 0.1
  5. > CLRS [Enter] will clear all precipitation totals
  6. Set up VRG101 in tipping output mode by > CONF 1 1 [Enter]. Note that there is a space between 1 and 1
  7. Make sure output messages are stopped. Type > AMES -1
  8. > CLOSE to close command line communication with VRG101

Program CR1000 or CR10X:

The following piece of CR10X code will allow the capture of data/pulse counts (assuming Pulse Channel was P2):

5: Pulse (P3)
1: 1 Reps
2: 2 Pulse Channel 2
3: 2 Switch Closure, All Counts
4: 3 Loc [ Rain_mm ]
5: 0.1 Multiplier
6: 0 Offset

Code for CR1000 will look like this (assuming Pulse Channel was C2):

PulseCount (Rain_mm, 1, 12, 2, 0, 0.1, 0)


  1. Mr. Hölttä from Vaisala was instrumental in getting us started with VRG101. Emails were returned quickly with accurate instructions and explanation. He made us realize the simplicity and beauty of the product. Mr. Hölttä's assistance was the most critical part in getting VRG101 working for us. He is very knowledgeable and his willingness to assist at the earliest is very impressive.
  2. Mr. Cole from Vaisala was instrumental in explaining how VRG101 works with CR10X. Mr. Cole actively shared his experiences with VRG101
  3. Mr. Merkel from Vaisala was our primary contact for the purchase of VRG101
  4. Mr. Knox from Campbell Scientific Inc for sharing his knowledge of CR10X/1000's control and pulse ports

Note: Please go through the proper channel to seek assistance. Consult your Sales Engineer before purchasing VRG101 and ask him/her clearly about support options and how quickly support will be provided. If you are used to Campbell Scientific Inc's quick support, you might get frustrated if you do not get replies in a couple emails or phone calls. Should you be asked to get in touch with Mr. Hölttä, consider your problems solved almost immediately. Please ask him the right questions with as much information you have and as much experience of instrumentation that you may have.

Things that did not help/work:

  1. Manuals: Manuals may not help novice users much. Consult an electrical or instrumentation engineer
  2. Calling Vaisala's US divisions: Calling Vaisala has not helped much. If you ever call Vaisala, please make sure you ask them if they know all about VRG101. Please be patient with emails that are replied with a couple of attachments that you already have in printed format and email body that says something along the lines of "Between the attachment and the VRG101 manual you should be able to set yours up." Easier said than done. Apparently, there are problems with the manual that I will include shortly
  3. Emailing hmehelp: This support email is slow and hardly replies with an accurate answer. It is advised by Vaisala to Cc this email, but in my personal opinion, it does not help the user who needs answers fairly quickly. A good manual would compliment this nice equipment. When emailing hmehelp, include what works, what does not work, instrument etc (refer to WHP25 manual page 22).


  1. WHP25 manual:
    1. Page 11: Figure 3 is not legible. Bigger and crisper image, preferably colored, might help
    2. Page 11: The good thing about Figure 4 is that it is clear and well labeled. X1 and X4 are good labels for terminal strips
    3. Page 12: Figure 5 is not legible. Bigger and crisper image, preferably colored, might help
    4. Inclusion of an example of how WHP25 works with VRG101 (if it is sold with VRG101) would help. Example of wiring WHP25 with WAC151 and WA25 may not be helpful to users who do not use them

      Informational note: If RS-485's brown conductor is connected to datalogger's 12V, there may be redundant power supply wiring now between the VRG101 and CR1000. The WHP25 is supplying some 24VDC (this voltage is higher when the heater is not active) to the VRG (XRM101)'s +VB and GND terminals. The power supply is also connected through the RS485 cable (brown wire) to CR1000. There is an internal diode in the XRM101 between the +VB terminal and the brown wire of both the RS232 and
      RS485 connectors. This diode will allow the 24VDC power supply current to flow from the +VB input to the RS232 and RS485 connectors but not vice versa. The described connection is totally OK if the intention is to power CR1000 from the WHP25 (assuming the logger tolerates 24VDC or a bit more). However, if CR1000 has its own independent power supply, the brown wire can (should) be removed from the 12V terminal of the Campbell and isolated with heat shrink etc.

      It is also totally possible to power the XRM101 from the Campbell logger if the 12V terminal supplies +12V. In that case, the wires from the WHP25 to the GND and +VB screw terminals of the XRM101 can be removed. The power for the XRM101 electronics will now be supplied through the blue and brown wires of the RS485 cable. The XRM101 requires only about 30mW to operate so the current consumption from the 12V terminal will be below 3mA.

  2. WHP25 instrument:
    1. X4 terminal block is a little tough to remove. It is easy to re-seat, though
  3. VRG101 manual:
    1. Page 16: Mentions about automatic messaging not available when VRG is on tipping bucket mode. It would be nice to mention that users can still use the STA or MES 2 command
    2. Page 17: Mentions about pull up resistor. What is this and how can one use it? What is the deal with jumper and what does a jumper look like?

      Informational note: The pulse output of the VRG uses the built in RS485 transmitter and as such has differential output. This means, when the pulse occurs, one of the signal pins jumps to +3V and the other drops to GND. When there is no activity, both of the pulse output wires are floating. If CR1000 cannot detect this sort of signal or there are GND reference problems, the XRO111 helps by adding optoisolation and making the output look like a switch closure from CR1000 point of view. Depending on the power supply arrangement, keeping the blue wire connected to the logger may or may not be required (but does not harm anything if it is connected)

      The RS485 direct output drives the pulse up and down actively, whereas the XRO111 output imitates a switch closure. There are two possible alternatives to add the pull up resistor. The first is to use the one internal to the XRO111. To access it, the top part of the XRO needs to be opened. Push the two clips on the sides and the top will pop open a millimeter. You can then slide the top part up with the PCB. The pull up jumper is the only jumper block in there and it needs to be shorted to enable the resistor. This resistor is internally connected between the Out+ and the VBin terminals of the XRO111 output side. This means that the VBin needs to be connected to a positive voltage source for the resistor to have any effect (check Campbell's recommendations for the correct voltage source).

      The other alternative is to enable a pullup in the CR1000 side if it has one. I do not know the CR1000 well enough so I don't know if a pull up is available for the C2 control port. Campbell might just be using external resistors. Note that in the XRO111 case the C2 port input will be held at positive voltage most of the time by the pull up resistor. When the tip pulse arrives, the XRO111 will pull the input low momentarily, just like a common tipping bucket does. The connection that works now applies a 3V positive pulse (white RS485 wire) to the C2 input when a tip occurs. This is of course totally reverse polarity compared to a normal tipping bucket so the CR1000 might need a slight programming change for the XRO111 to work.

    3. Page 28: Mentions about using either an external power connector or RS-485 or RS-232. Tables are provided, but it is difficult to infer its use. Table 2 mentions about pin numbers and description. +VB takes input voltage between 8 and 31 VDC. GND goes to ground. If Drain+ and Defrost+ need not be connected, it would be nice to see a mention of that. What is the use of Defrost- and Drain-? How does one use that?

      Informational note: The Drain and Defrost outputs at the XRM101 terminal strip are control outputs for future options. For example, a drain pump can be driven through Drain+ and Drain- outputs.
    4. Page 29: Mentions of Table 3 and 4. In the above context of supplying power, how should one use RS485 or RS232? What is SD+ and SD-, and what do they stand for in RS485 table? Examples of its application would be helpful

      Informational note: In the RS485 connector, SD+ means Serial Data positive and SD- Serial Data negative accordingly. With pulse output mode the pulse appears between these terminals instead of serial data.
    5. Where is the wiring diagram of WHP25 and VRG101?
    6. Page 32: Pulse Output Module (XRO111) is detailed on this page. What terminals on VRG connects to XRO111?
    7. Why is there no mention of XRO111's usage. Where does Out+, Out-, GND and +VBin connect? What is VB, by the way?

      Informational note: In Vaisala devices and documentation VB or +VB generally means Battery Voltage which in turn is +11 ... +15V unless otherwise specified (with the XRM101, the voltage
      range is wider).
    8. Command line portion is very well explained
  4. VRG101 instrument:
    1. Terminal strip is a little difficult to remove. It is easy to re-seat, though
    2. XRO111's terminal strip is easy to remove once a user knows how to remove it
    3. Calibration of VRG is great. It is easy to test calibration too


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