<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div><div>Hello Melaku,</div><div><br></div><div>I am forwarding this to the sac-help list in the hopes that it may garner the attention of more expertise.</div><div><br></div><div>Your calculation of CONSTANT looks generally correct with the exception of the 2*pi, it should not be included.</div><div><br></div><div>A standard gain STS-2 should be nominally 1500 Volts/meters/second, which needs to be scaled if you want nanometers. I have no idea what the digitizer gain for a RefTek 130 is, but lets assume your number is correct for now.</div><div><br></div><div>CONSTANT = A0 * SensorGain * Digitizer Gain</div><div><br></div><div>CONSTANT = 5.92e+07 * 1500 / 1.589e-06 = 5.588e+16 (so it looks like 2*pi is not in there after all).</div><div><br></div><div>That CONSTANT results in units of meters. So scale it by a factor of 1e9 for nanometers = 5.588e25</div><div><br></div><div>Hopefully someone more knowledgeable will correct any mistakes I've made.</div><div><br></div><div>On a slight related note, the poles and zeros you are using are the "truncated"/"simplified" STS-2 response and not the STS-2 nominal responses (you can access the nominal responses for each of 3 generations of STS-2 here: <a href="http://www.iris.edu/NRL/sensors/streckeisen/streckeisen_sts2_sensors.html)">http://www.iris.edu/NRL/sensors/streckeisen/streckeisen_sts2_sensors.html)</a>. This is not a critical problem unless you are working with high frequency data, I have heard that it's not important below 35 Hz.</div><div><br></div><div>Chad</div><div><br></div><div><div>On Apr 9, 2009, at 3:11 PM, Melaku Ayenew wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hello Chad,<br>Thank you for your response <br>I am just starting to learn sac for my research, I was trying to remove STS-2 broadband instrument and convolute the Wood-Anderson response. This is the STS2.pz file I came up with would you check it for me please<br> <br>ZEROS 2 (rad/sec)<br>0.000 0.000<br>0.000 0.000<br><br>POLES 5 (rad/sec)<br><br>-0.03701 0.03701<br>-0.03701 -0.03701<br>-251.3 0.0000<br>-131.0 467.30<br>-131.0 -467.30<br><br> CONSTANT 5.5884E+16<br><br>This is how I calculate the the Constant <br>CONSTANT=A0 X SensorGain X Digitizer Gain X 2*pi<br>Where A0 is normalization factor =5.92 E+07<br>The digitizer is REF TEC 130 data logger with bit weight 1.589E-06volts which I figure the digitizer gain would be 1/1.589 E-06 ( I am not sure about this step)<br> <br>And from SAC>transfer from polezero subtype STS2.pz to WA<br><br>when I plot this I got a waveform with amplitude in the order of 10E-4 nm (transfer returns values in nm)<br><br>I really appreciate your help.<br>Thank you in advance.!!<br> <br><br><br>Melaku Bogale<br> New Mexico State University<br> Department of Physics<br> Las Cruces NM 88003-8001<br><br><br> <br><br><div class="gmail_quote">On Wed, Apr 8, 2009 at 10:13 PM, Chad Trabant <span dir="ltr"><<a href="mailto:chad@iris.washington.edu">chad@iris.washington.edu</a>></span> wrote:<br> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br> Hello Melaku Bogale,<br> <br> You need to know the total sensitivity of the digitizer, this is the value which relates digital counts to ground units. The poles and zeros only represent the sensor. The CONSTANT in the SAC poles and zeros file should be the total sensitivity multiplied by the normalization factor for the poles and zeroes. The value for CONSTANT depends on the units desired also.<br> <br> Chad<br> IRIS DMC<div><div></div><div class="h5"><br> <br> On Apr 8, 2009, at 3:50 PM, Melaku Ayenew wrote:<br> <br> </div></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><div></div><div class="h5"> Hi All,<br> I am trying to remove instrument responses from STS_2, CMG3T. CMG_ES broadband instruments. I got the poles and zeros from IRIS Pascal Instrumentation. But I have difficulty figuring out what constant I should use in the *.pz file that has to read by the SAC TRANSFER command. For example, I was trying to synthesis a WA seismogram by removing the STS_2 response and convoulating the WA response. I used a constant of 1 in this calcultion. The synthesis seismogrm looks good but the displacemnt values don't make sense (they are several hunderd meters). I understand it is because of the CONSTANT=1 I put. My Question is How can I calculate the correct CONSTANT that I need to put with the zeros and poles in the SAC *.pz file. The IRIS PASCAL instrumentation page gives the zeros and poles and a normalization factor.<br> I greatly appreciate your help in this matter.<br> <br> Melaku Bogale<br> New Mexico State University<br> Department of Physics<br> Las Cruces NM 88003-8001<br></div></div> _______________________________________________<br> sac-help mailing list<br> <a href="mailto:sac-help@iris.washington.edu" target="_blank">sac-help@iris.washington.edu</a><br> <a href="http://www.iris.washington.edu/mailman/listinfo/sac-help" target="_blank">http://www.iris.washington.edu/mailman/listinfo/sac-help</a><br> </blockquote> <br> </blockquote></div><br></blockquote></div><br></body></html>